Read aquarium heater size ratings carefully

Follow the maker-stated maximum as a threshold

TH-C capacity boundaries: The exact-page maximums for TH-C100/200/300/400/500 are 35/55/100/125/150 gallons, respectively. Each remains at its inclusive maximum and leaves the upper-capacity result one gallon above. TH-C800 is listed to 270 gallons, while the questionnaire stops at 265; its full manufacturer ceiling is therefore outside the form. 35 gallons / 36, 55 / 56, 100 / 101, 125 / 126, 150 / 151, and the largest accepted form volume hold all other answers open. See the exact six-model TH-C table.

Decision: The manual maximums are 200 gallons for TTH-1000 and 300 for TTH-1500; AquaTop separately states up to 270 gallons for the first-generation TH-800W/DDC-800. The TTH product pages instead say 200–300 / up to 300 and 300–500 / up to 500, respectively, so the size-band claims conflict with their manuals and the max-only matcher cannot enforce either lower band. All three new exact products therefore remain reference-only, with no tank-minimum inference; the 270- and 300-gallon thresholds also exceed the public form's 265-gallon ceiling. Check the same four choices at 200 gallons, 201 gallons and the form's 265-gallon upper endpoint. Compare the source assessments for TTH-1000, TTH-1500 and first-generation TH-800W/DDC-800 with the active TH-C800. These are source screening limits and evidence gaps, not capacity test results.

The model-specific assessments are TH-C100 (35-gallon maximum), TH-C200 (55), TH-C300 (100), TH-C400 (125), TH-C500 (150) and TH-C800 (270; the public form reaches only 265).

Largest supported volume result: At 265 gallons, TH-C800 is the only current volume-only match; the smaller TH-C sizes and both EHEIM e300 types are outside their documented ceilings. The questionnaire cannot test AquaTop's actual 270-gallon TH-C800 maximum. Open the largest supported volume input and read the TH-C800 review.

For the lower boundaries, read the separate EHEIM e25 and classic Jäger 25 W assessments at 6/7 gallons, compare EHEIM e50 with Jäger 50 W at 15/16, and compare e75 with Jäger 75 W at 26/27; similar maxima do not mean the same control design or body dimensions.

The reviewed catalog has distinct maxima: 2.5 US gal (Aqueon Flat 5 W), 3 (Aqueon Flat 7.5 W and Fluval P10), 6 (P25), 6.6 (EHEIM e25/Jäger 25 W), 13 (HTG-50), 15 (GH PRO 50 W; Fluval E50/M50/P50/T50), 25 (HTG-100), 15.8 (EHEIM e50/Jäger 50 W), 26.4 (EHEIM e75/Jäger 75 W), 30 (GH PRO 100 W; Fluval M100/E100/T100), 39.6 (EHEIM e100/Jäger 100 W), 45 (Fluval M150/T150), 53 (EHEIM e125/Jäger 125 W), 40 (HTG-200, conservative older official figure; current exact page says 50), 55 (GH PRO 200 W), 60 (HTG-300, conservative older official figure; current exact page says 80), 65 (Fluval E200/M200/T200), 79 (classic e150/Jäger 150 W and separate thermocontrol+ e 150 Type 3666), 80 (GH PRO 300 W; Fluval M300/T300), 100 (HTG-400 conservative older official figure; current exact page says 130; Fluval E300), 106 (classic e200/Jäger 200 W and thermocontrol+ e 200 Type 3667), 159 (classic e250/Jäger 250 W and thermocontrol+ e 250 Type 3668), 260 (current-linked-manual Jäger 300 W) and 264 gallons (classic e300 and thermocontrol+ e 300 Type 3669). The GH PRO values belong to four distinct quartz-glass SKUs—GHPRO-050W, GHPRO-100W, GHPRO-200W and GHPRO-300W—not same-wattage conventional GH rows. The Aqueon 7.5 W's exact current page says 1–3 gallons, and the manual/catalog give up to 3; its linked chart conflicts by marking 1 gallon not recommended and 5 recommended, so confirm the item-specific packaging for a one-gallon tank. For the Aqueon 5 W, the current product page, package and chart say up to 2.5 gallons while a 2025 catalog row says 2; verify the exact package and instructions because those source records conflict. The 15 W Aqueon reference page documents 4–10 gallons but is not counted in finder results because the current matcher cannot enforce that four-gallon lower limit. The new WLAN models are not the classic e models even where maxima overlap. A capacity rule screens only an upper limit; it does not establish heat sufficiency in a particular room or certify an exact temperature.

The seven OASE US HeatUp SKUs have separate OASE technical maxima of 25, 50, 100, 150, 200, 300 and 400 L. Their U.S. product copy also states 10, 15, 30, 40, 55, 80 and 106 US gallons. This edition screens them at the lower litre-derived values—6.6, 13.2, 26.4, 39.6, 52.8, 79.3 and 105.7 US gal—rather than rounding up to the marketing figures. The 25 L/10 gal pair is especially far apart. Review the seven exact 25 W, 50 W, 100 W, 150 W, 200 W, 300 W and 400 W records or the family comparison before using a rounded endpoint.

Decision: Fluval M200/A784 has an exact 65-US-gallon inclusive rating: at 65 US gallons, it remains in the upper-capacity shortlist; at 66 gallons, it is screened out while the distinct M300 remains within its own 80-gallon maximum. Read the M200 assessment and compare the M300. These are ceiling screens, not proof of sufficient heater output for any room or smaller aquarium.

Decision: At 15 US gallons, 63 models remain within a stated maximum; at 16 gallons, 56 remain after seven products cross their separate 15-gallon ceilings: GH PRO 50 W, classic Jäger 50 W, thermocontrol e50 and Fluval E50, M50, P50 and T50. The other AquaTop capacities and larger models retain their own screens. The five additional OASE 100/150/200/300/400 W sizes pass both volume checks under their separate conservative capacity limits; compare their individual capacities. At 6 gallons, EHEIM e25 and Jäger 25 W are within their 6.6-gallon maxima, and all seven OASE, seven conventional GH, four GH PRO, five guarded HTG and three EX sizes pass their maximum-only screens. At 7 gallons, those EHEIM models, P25 and HeatUp 25 leave, while all nineteen AquaTop GH, GH PRO, HTG and EX sizes remain. Neither AquaTop series publishes a minimum tank size, so this is not a small-aquarium suitability conclusion. Jäger 75 W and e75 are within 26.4 gallons at 26 gallons, but both leave at 27; GH-100W and HTG-100 have separate 25-gallon ceilings, while each larger GH PRO/HTG size remains within its own separately documented upper screen. At 15/16 gallons compare Jäger 50 W/75 W with the distinct e50/e75; Type 3615 / Jäger 125 W and e125 each reach their separate maximum at 53 gallons but are out at 54; conventional GH-200W has already left above 50 gallons while GH PRO 200 W remains through 55, and GH PRO 300 W remains through 80. Review the EHEIM family comparison for exact Type identities. These matcher results screen upper limits only; approximate lower tank ranges and room conditions still matter.

Decision: The four distinct GH PRO quartz-glass configurations have inclusive volume ceilings of 15, 30, 55 and 80 US gallons for 50/100/200/300 W respectively. GH PRO 50 W is included at its 15-gallon ceiling and excluded at 16 gallons. GH PRO 100 W is included at its 30-gallon ceiling and excluded at 31 gallons. GH PRO 200 W is included at its 55-gallon ceiling and excluded at 56 gallons. GH PRO 300 W is included at its 80-gallon ceiling and excluded at 81 gallons. Compare their exact 50 W, 100 W, 200 W and 300 W reviews with similarly named conventional GH models; upper-capacity filters do not certify a minimum size or heat performance.

Decision: The OASE technical capacities convert to seven conservative integer boundaries: HeatUp 25 remains within the source screen at 6 gallons and leaves at 7; 50 W is within at 13 and out at 14; 100 W is within at 26 and out at 27; 150 W is within at 39 and out at 40; 200 W is within at 52 and out at 53; 300 W is within at 79 and out at 80; and 400 W is within at 105 and out at 106. Each link changes only the numeric volume answer. These upper-limit screens do not establish a safe minimum tank size or heating performance; compare each linked OASE model rating and body length separately.

Interaction: At 6 gallons, all seven OASE models, seven conventional AquaTop GH sizes, four GH PRO sizes, five HTG sizes and three EX sizes pass the upper-capacity condition, but neither AquaTop series publishes a minimum aquarium size; that result is not evidence that a larger heater is suitable for a very small tank. With freshwater, in-tank installation, adjustable control and a 78°F setting held constant, see the 6-gallon combined result; compare conventional GH-50W with distinct GH PRO 50 W and 300 W configurations. At 7 gallons, all nineteen AquaTop GH, GH PRO, HTG and EX sizes remain within their separate upper limits; the OASE 25 W model leaves while its 50 W and higher sizes remain; see the same other conditions at 7 gallons. Because the current finder has no lower-capacity rule, verify manufacturer instructions and independent sizing before treating a larger unit as a fit.

Compare the separately named EHEIM electronic families at their own limits: classic e e150/e200/e250/e300 and WLAN thermocontrol+ e Type 3666/3667/3668/3669. Their similar wattages do not make their Type numbers, dimensions or controls interchangeable.

At 39 gallons the volume-only library has 44 candidates, including conservative HTG-200/300/400, EX-200/300, GH PRO 200/300 W, OASE HeatUp 150/200/300/400 W, Jäger 100 W and larger sizes plus EHEIM e100/e125; at 40 gallons there are 41, as the 100 W Jäger, electronic e100 and HeatUp 150 pass their respective 39.6-gallon conservative ceilings. At 79 gallons, 23 volume-only models remain, including HTG-400, GH PRO 300 W, HeatUp 300/400 and the separate thermocontrol+ e Type 3666; at 80 gallons, HeatUp 300 and Type 3666 leave, leaving 19 while HTG-400, GH PRO 300 W and HeatUp 400 remain inside their separate screens. At 81 gallons GH PRO 300 W, Fluval M300 and T300 leave their 80-gallon maxima, bringing the volume-only result to 16. These thresholds belong to distinct types, not thermal performance.

At 100 gallons, 16 volume-only models remain, including HTG-400 at the conservative capacity endpoint and HeatUp 400; at 101 gallons, HTG-400, TH-C300 and Fluval E300 leave their separate ceilings, leaving 13 while HeatUp 400 remains below its 105.7-gallon conservative screen. The separate EHEIM Type 3667, classic e200 and Jäger Type 3617 share a 106-gallon ceiling: 106 gallons returns 12, and 107 removes all three, leaving nine. At 159 gallons, seven candidates remain, including classic Jäger 250 W and both 250 W EHEIM families; at 160, those three 250 W models leave and four candidates remain. The classic e300 and thermocontrol+ e300 reach 264 gallons; three models remain at that boundary, including AquaTop TH-C800, and 265 gallons leaves TH-C800 as the only active volume-only match.

For a direct look at one of the larger thresholds, compare classic EHEIM thermocontrol e200 / Type 3637 with WLAN thermocontrol+ e200 / Type 3667; each has its own 106-gallon source row and product review.

At 265 US gallons the AquaTop TH-C800 is the only active volume-only match; the classic thermocontrol e300 and thermocontrol+ e300 have each reached their separate 264-gallon limit. The Finnex TH-800S is still a reference-only tube, not an active plan, because the separate controller and lower-volume limit cannot be fully applied. This result is limited to the reviewed library, not every heater on the market.

A capacity boundary is useful only when tied to the exact source row. The classic Jäger Type 3614–3619 limits remain 39.6, 53, 79, 106, 159 and 260 US gallons in the current linked manual. The separate thermocontrol+ e Types 3666–3669 add 79, 106, 159 and 264 gallon maxima; the official manual provides each Type row and those exact identity/capacity differences are not inherited from classic e products.

Volume-only witness: At 39 gallons the reviewed set has 44 candidates, including conservative HTG-200/300/400, EX-200/300, GH PRO 200/300 W, OASE HeatUp 150/200/300/400, Jäger 100 W and larger sizes plus EHEIM e100/e125; at 40 gallons there are 41 after HeatUp 150, Jäger 100 W and e100 exceed their 39.6-gallon conservative ceilings. This is a capacity-only screen: compare the distinct HeatUp 150, Jäger 100 W, thermocontrol e100 and e125 reviews rather than treating equal counts or wattage labels as interchangeable.

Decision: At 2 US gallons, 64 reviewed heaters remain in the upper-capacity screen, including Aqueon Flat 5 W and 7.5 W, all seven OASE HeatUps, seven conventional AquaTop GH sizes, four separate GH PRO models and all five HTG glass/guard configurations under their maximum-only screens. AquaTop does not state a minimum volume for HTG, so that screen does not establish a small-tank recommendation. The 5 W page/package/chart say up to 2.5 gallons while a 2025 catalog row says 2, so verify that exact package; the 7.5 W page says 1–3 gallons but its linked chart marks 1 gallon not recommended. The integer finder cannot express the 5 W half-gallon ceiling; use the 2-gallon upper-capacity result and inspect the 5 W, 7.5 W, GH PRO 50 W and HeatUp model limits. The 15 W Aqueon reference is not a matcher candidate because its exact range starts at 4 gallons. A capacity-only result does not establish heat sufficiency in any room or a minimum safe tank size.

Decision: At 3 US gallons, 66 matcher candidates remain in the maximum-only result, including five HTG upper-capacity screens with no documented minimum-volume bound. The Aqueon Flat 5 W leaves above its current 2.5-gallon maximum, while the Aqueon 7.5 W remains within its exact-page 1–3 range and Model 01230's manual/catalog 3-gallon ceiling; the linked manufacturer chart conflicts at 1 gallon and 5 gallons, so check its exact item instructions. The other 61 capacity records, including the seven OASE, seven conventional GH, four GH PRO, five HTG and three EX maximum-only screens, remain in this capacity-only result. See the same volume filter at 3 gallons, compare the Aqueon 5 W source conflict and 7.5 W chart discrepancy with the P10's separate 3-gallon ceiling and the OASE model maxima, and do not interpret a maximum as a heating guarantee.

Decision: At 2 US gallons with in-tank placement and a required shatterproof body, five reviewed models remain: Aqueon Flat 5 W, Aqueon Flat 7.5 W and Fluval P10, P25 and P50. At 3 gallons, the 5 W model leaves but the 7.5 W's current page/manual maximum of 3 gallons keeps it within the result; the HTG glass heaters do not pass this shatterproof-body requirement, despite their protective guards. The linked Aqueon recommendation chart conflict is described in the review. The quartz HeatUp tubes, seven conventional GH glass bodies and four separate GH PRO quartz-glass bodies are not documented as shatterproof and do not pass this added body requirement. Check the 2-gallon combined result and the same requirements at 3 gallons; compare the Aqueon 5 W and 7.5 W reviews for their distinct wattages and source limits.

AquaTop GH capacity witnesses: The exact GH rows use upper limits of 13/20/25/40/50/65/75 gallons. With the volume-only question held on its own, GH-50W is included at 13 gallons and excluded at 14; GH-75W at 20 but not 21; GH-100W at 25 but not 26; GH-150W at 40 but not 41; GH-200W at 50 but not 51; GH-250W at 65 but not 66; and GH-300W at 75 but not 76. Read the individual 50 W, 75 W, 100 W, 150 W, 200 W, 250 W and 300 W assessments. GH-300 uses the exact technical/manual/data-sheet 75-gallon figure rather than the collection's 80-gallon headline. No minimum GH volume is documented; an upper-limit pass is not evidence that a heater is appropriate for a much smaller aquarium.

Decision: With volume as the only entered need, GH-100W is within its 25-gallon ceiling at 25 gallons and leaves at 26 gallons. GH-200W is included at its 50-gallon ceiling in the 50-gallon result and leaves above it at 51 gallons. Compare the separate GH-100W, GH-200W and GH-250W capacity records.

Interaction: With freshwater, 200 gallons, in-tank placement and adjustable control, the active matcher returns four products: TH-C800, Jäger 300 W, thermocontrol e300 and thermocontrol+ e300. At 201 gallons, the same four remain. The TTH-1000, TTH-1500 and first-generation TH-800W/DDC-800 do not join either result: their page/manual capacity conflicts, unrepresented lower bands or unknown minimum scope keep them reference-only. Check the exact four conditions at 200 gallons and at 201 gallons. These are upper-limit screening results, not a minimum-volume or heating-performance recommendation.

Six additional Jäger size boundaries

The Type 3614 Jäger 100 W row has a 39.6-US-gallon maximum: at 39 gallons it remains in the upper-capacity screen, while at 40 gallons it does not. Compare its separate 100 W / Type 3614 review with Type 3615 / 125 W at the larger side. This does not establish that either wattage is ideal for a smaller tank.

For Type 3615 / Jäger 125 W, 53 gallons is the manual's inclusive maximum and 54 gallons is beyond it; inspect the 125 W assessment and next-size 150 W review. Type 3616 / Jäger 150 W reaches 79 gallons, but not 80; the next model's Type 3617 / 200 W review records a distinct 106-gallon ceiling.

Type 3617's Jäger 200 W row remains through 106 gallons and leaves at 107; at the latter, compare its review with Jäger 250 W / Type 3618. Type 3618 has its own inclusive 159-gallon limit, while 160 exceeds it; the individually assessed Jäger 300 W / Type 3619 has the next larger listed range.

For Type 3619 / Jäger 300 W, the current EHEIM manual linked from the exact product page gives 260 US gallons; the integer questionnaire excludes this model at 261. An archived official manual and a retailer entry instead say 264 gallons, so this guide uses the lower current linked-manual value and flags the discrepancy in the model review. The EHEIM e300 has a separate 264-gallon Type 3639 limit; it is not evidence that the Jäger Type 3619 shares it.

Decision: Type 3666 / thermocontrol+ e 150 is within its manual's 79-US-gallon ceiling at 79 gallons, but is above its limit at 80; Type 3667 / 200 W remains below its separate 106-gallon maximum. Compare the Type 3666 review at the boundary with the next-size Type 3667 review.

Decision: Type 3667 / thermocontrol+ e 200 has an inclusive 106-US-gallon maximum at 106 gallons, and is removed at 107; the 250 W Type 3668 remains within its own larger band. Compare the Type 3667 and Type 3668 assessments.

Decision: Type 3668 / thermocontrol+ e 250 remains within its 159-US-gallon maximum at 159 gallons and is over that ceiling at 160; the 300 W Type 3669 has a separate 264-gallon limit. See the Type 3668 and Type 3669 reviews.

Decision: Type 3669 / thermocontrol+ e 300 reaches its 264-US-gallon manual ceiling at 264 gallons but not at 265; its matching classic e300 also ends at 264. Compare the exact Type 3669 review with classic e300 / Type 3639. No reviewed operating plan matches 265 gallons; this is a limit of the researched library, not proof that no product elsewhere exists.

Aqueon's four exact Preset manuals have distinct recommended bands: PS50H 50 W is 5–20 gallons, PS100H 100 W is 20–30, PS150H 150 W is 30–55, and PS200H 200 W is 55–75 gallons. The current volume rule tests an upper maximum only; it cannot enforce those four lower endpoints, so all four researched items are reference-only rather than finder results, even at a volume inside the printed band. Their upper values are still separately recorded from the exact model rows. The 100 W band is especially important to check: the current variant page, manual and 2025 catalog table say up to 30, while the exact package visual says 40 and the general 100 W chart spans 15–40. The review uses the model-specific 20–30 manual/page/table evidence and leaves the package conflict visible. See the separate PS50H 50 W, PS100H 100 W, PS150H 150 W and PS200H 200 W assessments. For active upper-limit comparisons, see the distinct Fluval M100, M150, M200 and M300 reviews; package dimensions are not installed clearance, and no ceiling predicts heating performance in a particular room.

Decision: The numeric finder cannot apply the Aqueon Preset manuals' 5-, 20-, 30- and 55-gallon lower boundaries; those exact models stay reference-only even where a selected volume falls within the printed band. Compare the visible numeric screen at 20/21, 30/31, 55/56, and 75/76 gallons. These are real upper-limit results for the reviewed matching set, not proof that a reference-only Aqueon model is a fit.

Decision: Aqueon's separate Mini Heater 10 W page lists a 2.5–5-gallon range, but because the current max-only volume rule cannot enforce its 2.5-gallon floor, the exact model remains reference-only and is not returned for any volume; inclusion would falsely match 1–2-gallon answers. See other in-tank matches under the same 5-gallon condition and read the Mini 10 W assessment. The active result counts above do not include this reference assessment.

Decision: The 2011 Aqueon Pro AP250W manual specifies a 65–90 US-gallon recommendation, but no current retail item/UPC is verified; the reference-only AP250W stays out of the finder at both 90 and 91 gallons, and AP300W-H is not an assumed substitute.

Use the same capacity-only finder input at 90 gallons and 91 gallons to inspect the full current candidate set; these screens do not include AP250W. The AP250W manual-reference assessment records its 65–90-gallon source range, and the Fluval E300 review is one distinct, current example within the 90-gallon upper-capacity result—not a husbandry or performance recommendation.

Finnex TH tube bands: profile them, do not treat them as complete matches

Finnex's TH family table assigns TH-300S, TH-500S and TH-800S distinct 40–80, 70–130 and 140–265 US-gallon bands. Its standalone shop page calls the offering a titanium tube only and says controllers are sold separately. Since each band has a lower endpoint and the current volume rule checks only a maximum, these three documented rows stay reference-only; none is returned as a complete heater choice. A candidate elsewhere in a volume-only result is a separate configuration, not a presumed controller-and-tube substitute.

Decision: At 39 US gallons, the Finnex TH-300S is below its published 40–80-gallon band and remains reference-only; the volume-only finder has 44 active candidates, including AquaTop EX-200/300, Fluval E200 and OASE HeatUp 150/200/300/400. Try the same volume-only finder input at 39 gallons, review the TH-300S reference, and compare HeatUp 150 with the separate Fluval E200.

Decision: At 40 US gallons, the TH-300S reaches the lower endpoint of its published 40–80-gallon band but remains reference-only because the current matcher cannot enforce that floor and the standalone tube requires a separate controller; the volume-only finder has 41 active candidates, including AquaTop EX-200/300, Fluval E200 and HeatUp 200/300/400. Try the same volume-only finder input at 40 gallons; the separate TH-300S reference and Fluval E200 review describe different setups.

Decision: At 69 US gallons, the Finnex TH-500S is below its published 70–130-gallon band and remains reference-only; the volume-only finder has 25 active candidates, including EHEIM Jäger 200 W, AquaTop EX-300 and OASE HeatUp 300/400. Use the same volume-only finder input at 69 gallons, then compare the TH-500S reference with the separate Jäger 200 W assessment.

Decision: At 70 US gallons, the TH-500S reaches its published lower endpoint but remains reference-only because the current matcher cannot enforce that floor and the standalone tube requires a separate controller; the volume-only finder has 25 active candidates, including EHEIM Jäger 200 W, AquaTop EX-300 and OASE HeatUp 300/400. Check the same volume-only finder input at 70 gallons and read the distinct TH-500S reference and Jäger assessment.

Decision: At 80 US gallons, the TH-300S reaches its published upper endpoint but stays reference-only; the volume-only result has 19 active candidates, including Fluval M300 and OASE HeatUp 400, and none is the tube-only configuration. See the same volume-only finder input at 80 gallons, the separate TH-300S reference and M300 review.

Decision: At 81 US gallons, the TH-300S is above its published maximum and remains reference-only; the 16-model volume-only result no longer includes Fluval M300, while EHEIM Jäger 200 W and OASE HeatUp 400 remain. Check the same volume-only finder input at 81 gallons and compare the separate TH-300S reference with Jäger 200 W.

Decision: At 130 US gallons, the TH-500S reaches its published maximum but remains reference-only; the eight-model volume-only set includes EHEIM Jäger 250 W and does not include the tube. See the same volume-only finder input at 130 gallons and the distinct TH-500S reference and Jäger 250 W review.

Decision: At 131 US gallons, the TH-500S is above its published maximum and remains reference-only; the same eight active volume-only candidates, including EHEIM Jäger 250 W, remain because no active model has this exact threshold. Use the same volume-only finder input at 131 gallons, then check the separate TH-500S reference and Jäger review.

Decision: At 139 US gallons, the TH-800S is below its published 140–265-gallon range and remains reference-only; the eight-model volume-only result includes EHEIM Jäger 250 W instead. Check the same volume-only finder input at 139 gallons and compare the TH-800S reference with the distinct Jäger 250 W assessment.

Decision: At 140 US gallons, the TH-800S reaches its published lower endpoint but remains reference-only because the matcher cannot enforce that floor and the standalone tube requires a separate controller; eight active volume-only candidates, including EHEIM Jäger 250 W, remain. See the same volume-only finder input at 140 gallons, the TH-800S reference and the distinct Jäger review.

Decision: At 264 US gallons, the TH-800S is within its 140–265-gallon published band but remains reference-only; the volume-only finder returns three active models: the distinct EHEIM e300 and thermocontrol+ e300 candidates plus AquaTop TH-C800. Check the same volume-only finder input at 264 gallons, the separate TH-800S reference and the classic e300/WLAN e300 assessments alongside TH-C800.

Decision: At 265 US gallons, the TH-800S reaches its published upper endpoint but remains reference-only; the active volume-only result contains AquaTop TH-C800 only. Check the same volume-only finder input at 265 gallons and inspect the TH-800S reference before treating its tube-only table band as an actionable purchase assessment.

What remains at 265 gallons: TH-C800 is the one active volume-only match. The two EHEIM e300 configurations end at 264 gallons; Finnex's TH-800S remains reference-only because it requires a separate compatible controller and the finder cannot enforce its 140-gallon lower bound. This result is limited to this reviewed library, not every heater on the market.

Finnex THH tube bands: controller, floor and model size remain separate

Finnex's THH family overview links a three-row model table for distinct titanium tubes: THH-300S is 300 W and 40–80 US gallons with a 10.63-inch tube; THH-500S is 500 W and 70–130 gallons with a 14.57-inch tube; THH-800S is 800 W and 140–265 gallons with a 17.32-inch tube. The family requires a separate external temperature controller, warns against direct wall connection, says use only in water above 150 ppm TDS and calls for regular out-of-water-sensor checks. The current matcher can apply only a maximum, not those lower floors, and the exact control range, complete installation route and retail offers remain unknown. These source bands are therefore reference context, not complete configurations or finder recommendations; see THH-300S, THH-500S and THH-800S.

Decision: At 40 US gallons, the THH-300S reaches its published lower endpoint but remains reference-only because the matcher cannot enforce that floor and the separate controller and installation route are unresolved; the volume-only finder returns 41 active models, including Jäger 125 W and OASE HeatUp 200/300/400. At 39 gallons the THH-300S is below its published band and remains excluded; 44 volume-only candidates include Jäger 100 W and HeatUp 150/200/300/400. Check the same volume-only inputs at 40 gallons and 39 gallons, and compare the separate THH-300S reference with Jäger 125 W, 100 W and the HeatUp sizes.

Decision: At 80 US gallons the THH-300S reaches its published maximum but remains reference-only because its lower limit and controller/setup constraints cannot be fully applied; 19 volume-only candidates include Jäger 200 W and OASE HeatUp 400. At 81 gallons it is above its band and still excluded; 16 volume-only candidates include Jäger 200 W and HeatUp 400. Use the same volume-only finder input at 80 gallons and 81 gallons, then read the THH-300S reference and Jäger 200 W review.

Decision: At 70 US gallons the THH-500S reaches its published lower endpoint but remains reference-only because the matcher cannot enforce that floor; 25 volume-only candidates include AquaTop EX-300, Jäger 150 W and OASE HeatUp 300/400. At 69 gallons it is below its published band and remains excluded from the same 25-model screen. Compare the exact volume-only results at 70 gallons and 69 gallons with the separate THH-500S reference and Jäger 150 W review.

Decision: At 130 US gallons the THH-500S reaches its published upper endpoint but remains reference-only; the eight-model volume-only set includes Jäger 250 W. At 131 gallons it is above its band and stays excluded, while those same eight active candidates remain. Check the exact volume-only answers at 130 gallons and 131 gallons, and compare THH-500S with Jäger 250 W.

Decision: At 140 US gallons the THH-800S reaches its published lower endpoint but remains reference-only because the matcher cannot enforce that floor; six volume-only candidates include Jäger 250 W. At 139 gallons it is below the published band and still excluded from the same six active candidates. See the exact screens at 140 gallons and 139 gallons with the THH-800S reference and Jäger 250 W assessment.

Decision: At 264 US gallons the THH-800S is within its published 140–265-gallon band but remains reference-only; the volume-only finder returns three active models: the distinct classic e300, thermocontrol+ e300 and AquaTop TH-C800. At 265 gallons the THH-800S reaches its upper endpoint but remains reference-only; TH-C800 is the sole active volume-only model. Check 264 gallons and 265 gallons under the same volume-only condition; compare the THH-800S reference with classic e300, thermocontrol+ e300 and TH-C800. This result is limited to this reviewed library, not every heater on the market.

At 80 US gallons with freshwater, in-tank installation, adjustable control and a 90°F target, 18 reviewed matches remain, including HTG-400, the distinct GH PRO 300 W at its inclusive 80-gallon ceiling, Fluval T300 and OASE HeatUp 400; THH-300S remains excluded as a reference-only tube with unresolved controller and installation requirements. See the same five answers at 80 gallons. At 81 gallons with the other four answers unchanged, 16 matches remain; GH PRO 300 W and Fluval T300 have left their exact 80-gallon ceilings, while HTG-400 and HeatUp 400 stay below their own conservative ceilings; THH-300S remains excluded. Check the same five choices at 81 gallons. Compare the exact GH PRO 300 W review with THH-300S, HeatUp 400, Fluval T300 and Jäger 200 W; a tube's water-type and volume table do not answer whether its missing controller/installation documentation suits this whole plan.

Finnex HPC bands: read the lower endpoint too

Finnex's HPC manual gives three separate ranges: HPC-100 is 20–30 US gallons, HPC-200 is 60–80 gallons, and HPC-300 is 80–100 gallons. The manual's 30, 80 and 100 gallon ceilings are real upper-capacity boundaries, but the finder can only compare a chosen volume with a maximum. It cannot apply the respective 20, 60 and 80 gallon floors. These configurations therefore stay reference-only rather than appearing below their published ranges; the 200 W and 300 W bands meet at 80 gallons, but differ in wattage, current reference and listed length. No finder result is a heat-output guarantee.

Decision: At the exact HPC upper values—30 gallons for the HPC-100, 80 for the HPC-200 and 100 for the HPC-300—the same-condition volume-only finder does not turn those reference-only heaters into matches. Check 30 gallons, 80 gallons or 100 gallons, then compare the separate HPC-100, HPC-200 and HPC-300 source assessments. Finnex's manual and family page also leave the full installation method and approved water type unconfirmed, so a numeric capacity screen alone cannot settle those questions.

The five guarded-glass HTG models have individually different capacity thresholds, not one family-wide rating. AquaTop's current exact pages state 13, 25, 50, 80 and 130 US gallons for HTG-50/100/200/300/400; its older official HTG-50W/100W/200W/300W/400W table gives 13, 25, 40, 60 and 100. Because no version bridge resolves the larger three conflicts, this finder uses the conservative 13/25/40/60/100-gallon figures while keeping higher current-page values visible in each review. HTG-50 is included at its 13-gallon ceiling and excluded at 14 gallons; compare 13 gallons with 14 gallons. HTG-100 is included at its 25-gallon ceiling and excluded at 26 gallons; compare 25 gallons with 26 gallons. HTG-200 is included at its conservative 40-gallon ceiling and excluded at 41 gallons; compare 40 gallons with 41 gallons. HTG-300 is included at its conservative 60-gallon ceiling and excluded at 61 gallons; compare 60 gallons with 61 gallons. HTG-400 is included at its conservative 100-gallon ceiling and excluded at 101 gallons; compare 100 gallons with 101 gallons. These are upper-limit screens only. AquaTop publishes no minimum tank-volume bound for these models, and an in-range result is not evidence that a heater is appropriate for a smaller aquarium, its temperature differential or its livestock. Compare all five exact identities in the HTG comparison and inspect individual HTG-50, HTG-100, HTG-200, HTG-300 and HTG-400 sources.

The exact AquaTop TQ pages state maximums of 30 gallons for TQ-100W, 75 for TQ-200W and 85 for TQ-250W. Package photos show distinct bands of 15–30, 55–75 and 75–85 gallons; the pages and manual do not call the lower package endpoints minimum safe volumes. The current matcher can represent their upper thresholds but cannot make them conditional on those lower package edges, so all three remain references instead of finder candidates. For the upper-limit boundaries, compare the volume-only finder at 30 and 31 gallons for TQ-100W, 75 and 76 for TQ-200W, and 85 and 86 for TQ-250W. The package starts at 15, 55 and 75 gallons are useful sizing context, not safe-minimum claims; see the three-model comparison and each exact review.

HMH and HMS size bands: same capacity, different sensor installation

The separate HMH and HMS manuals give each family six exact wattage rows and the same successive US-gallon bands: 50 W, 10–20; 100 W, 20–30; 150 W, 30–60; 200 W, 60–80; 300 W, 80–100; and 500 W, 100–120. The shared bands do not make the models identical: HMH has a tube-mounted sensor, whereas HMS uses a remote water probe. Their individual tube lengths and lead lengths also vary by wattage and family; use the linked model reviews to check those exact dimensions.

The matcher tests an upper capacity only, so it cannot enforce the published 10/20/30/60/80/100-gallon lower edges for these rows. All twelve are reference-only because the complete supply rating and exact current retail configuration were not resolved, and no model is represented as a finder match even at the upper endpoint. The unconditioned finder links below show only the active reviewed library's same-volume result; they are not compatibility links for the HMH/HMS references or assurances of sufficient output.

• HMH-50S and HMS-50S: 50 W, 10–20 gallons. Read HMH-50S and HMS-50S; same volume-only condition at the 20-gallon ceiling.
• HMH-100S and HMS-100S: 100 W, 20–30 gallons. Read HMH-100S and HMS-100S; 30-gallon ceiling screen.
• HMH-150S and HMS-150S: 150 W, 30–60 gallons. Read HMH-150S and HMS-150S; 60-gallon ceiling screen.
• HMH-200S and HMS-200S: 200 W, 60–80 gallons. Read HMH-200S and HMS-200S; 80-gallon ceiling screen.
• HMH-300S and HMS-300S: 300 W, 80–100 gallons. Read HMH-300S and HMS-300S; 100-gallon ceiling screen.
• HMH-500S and HMS-500S: 500 W, 100–120 gallons. Read HMH-500S and HMS-500S; 120-gallon ceiling screen.

Finnex STE capacity bands stay model-specific

Finnex's official STE data table lists 40–60, 80–100, 120–150, and 190–265 US-gallon bands for STE-200, STE-400, STE-600, and STE-800, respectively; these are reference ranges, not verified finder recommendations. The 60-, 100-, 150- and 265-gallon endpoints are inclusive maker-stated maxima. The lower endpoints are 40, 80, 120 and 190 gallons, and the current matcher cannot enforce them. Each model therefore stays out of the active result set at all volumes rather than being shown below its stated floor.

• STE-200 (200 W): 40–60 gallons and 1.67 A; see the unconditioned 60-gallon finder set.
• STE-400 (400 W): 80–100 gallons and 3.33 A; see the unconditioned 100-gallon finder set.
• STE-600 (600 W): 120–150 gallons and 5 A; see the unconditioned 150-gallon finder set.
• STE-800 (800 W): 190–265 gallons and 6.67 A; see the unconditioned 265-gallon finder result.

Finnex's official gallery associates these electrical and volume rows with each exact model code, and its Shop selector independently identifies the four wattage-specific variants. The same manufacturer materials give the family an adjustable 68–92°F controller, freshwater/marine claim and titanium body. They do not establish the STE's full voltage/frequency label or installation instructions in the sources reviewed here. A volume result is not a prediction of heat sufficiency; check the exact heater label and supplied setup directions.

Fixed 78°F, saltwater, in-tank use and Aqueon's lower ranges

These are five simultaneous answers: saltwater, the actual volume shown, a submersible heater inside the aquarium, fixed-preset control and a 78°F setting. AquaTop GH, GH PRO and HTG heaters use adjustable dials rather than fixed presets, so none of these glass-and-guard sizes passes this control choice; compare the five HTG variants with the preset P and reference-only Aqueon models. At 5 gallons the matcher returns Fluval P25 and P50; PS50H's manual band begins at five gallons, but Aqueon remains reference-only because the same upper-only rule cannot prevent it appearing below five in other queries. At 20, 30, 55 and 75 gallons the combined query has no matcher candidate: Fluval's largest active P model is rated only up to 15 gallons, and the corresponding Aqueon sizes stay reference-only rather than bypassing their model-specific lower limits. These outcomes compare exact finder rules, not an endorsement of a 78°F husbandry target.

At 5 gallons with saltwater, in-tank installation, preset-only control and a 78°F target, the matcher returns Fluval P25 and P50; the PS50H remains a separate reference because the finder cannot enforce its 5-gallon minimum. See the same five-answer finder result. Compare the P25 and P50 with the separate Aqueon PS50H assessment.

At 20 gallons with the same saltwater, in-tank, preset and 78°F requirements, this reviewed matcher returns no candidate; the PS100H's 20-gallon minimum cannot be enforced and the active P sizes end below that volume. Check the same five answers at 20 gallons. The zero-result set is a gap in this site's reviewed matching library and current rule limitations, not proof that no other heater exists. See the reference-only PS100H review.

At 30 gallons with the same four nonnumeric requirements, this reviewed matcher returns no candidate; the PS100H reaches its manual's 30-gallon ceiling but remains reference-only because its 20-gallon floor cannot be applied. Check all five answers at 30 gallons. The zero-result set is a gap in this site's reviewed matching library and current rule limitations, not proof that no other heater exists. The separate PS150H manual starts at 30 gallons, and its reference review does not turn it into a finder match.

At 55 gallons with the same four nonnumeric requirements, this reviewed matcher returns no candidate; the PS150H's manual band ends at 55 and the PS200H's band begins there, but both remain reference-only because their lower limits cannot be enforced. Check all five answers at 55 gallons. The zero-result set is a gap in this site's reviewed matching library and current rule limitations, not proof that no other heater exists. Compare the separate PS150H and PS200H reference assessments.

At 75 gallons with the same four nonnumeric requirements, this reviewed matcher returns no candidate; 75 gallons is the PS200H manual's upper endpoint, but the model remains reference-only because its 55-gallon minimum cannot be enforced. Check all five answers at 75 gallons. The zero-result set is a gap in this site's reviewed matching library and current rule limitations, not proof that no other heater exists. Read the PS200H assessment for its exact package/manual checks.

Freshwater, adjustable control and a 65-gallon limit

For the EHEIM electronic comparison at these same freshwater/adjustable boundaries, see the separately reviewed e150, e200, e250 and e300; their electronic Type ratings differ from classic Jäger.

At 65 US gallons, 29 freshwater models with adjustable control have published maxima reaching that volume, including AquaTop GH-250W, GH PRO 300 W and EX-300; at 66 gallons, 25 remain after GH-250W and the Fluval E/M/T 200 W models cross their separate 65-gallon ceilings. At 79 gallons, 23 remain, including HTG-400, GH PRO 300 W and HeatUp 300/400; at 80, HeatUp 300, classic Jäger 150 W, electronic e150 and thermocontrol+ e Type 3666 leave their separate 79-gallon limits, leaving 19. Type 3667 reaches 106 but not 107, Type 3668 reaches 159 but not 160, and Type 3669 reaches 264 but not 265; those freshwater-adjustable totals are 12/9, 7/4 and 3/1 at the respective integer boundaries. At 265, TH-C800 is the only active freshwater-adjustable match. These are upper-limit screens, not heat-output predictions; the OASE pages do not give minimum tank sizes.

Decision: A 65-gallon freshwater tank needing adjustable control has 29 candidates, including guarded HTG-400 in its own 100-gallon conservative ceiling, GH-250W, GH-300W and separate GH PRO 300 W; at 66 gallons 25 remain after GH-250W and Fluval E/M/T 200 W cross their separate 65-gallon limits. See the 65-gallon combination and the 66-gallon result. The OASE HeatUp 300 and 400 both remain under their conservative maximums here. At 79 gallons, 23 remain; at 80, HeatUp 300, Jäger 150 W, thermocontrol e150 and Type 3666 leave their 79-gallon ceilings, leaving 19. See 79 gallons or 80. Compare the HeatUp capacity differences with EHEIM Type 3666 / 150 W and Type 3667 / 200 W; these are upper-capacity results, not proof of a lower-volume fit.

Decision: At 106 gallons, 12 freshwater adjustable models remain, including thermocontrol+ e Type 3667; at 107, classic e200, Jäger 200 W and Type 3667 leave their 106-gallon ceilings, leaving nine candidates. See 106 gallons and 107. Compare Type 3667 with Type 3668.

Decision: At 159 gallons, seven freshwater adjustable candidates remain, including the 250 W thermocontrol+ e Type 3668; at 160 that type, the matching 250 W classic e and Jäger 250 W are over their separate ceilings, leaving four. See the 159-gallon boundary and the same conditions at 160. Compare Type 3668 with 3669.

Decision: At 264 gallons, three freshwater adjustable candidates remain: classic e300, thermocontrol+ e300 and TH-C800. At 265, only TH-C800 remains active. See the 264-gallon limit or the first gallon above it, and compare Type 3669, Type 3639 and TH-C800. This scoped result does not describe every manufacturer.

The active 265-gallon match is TH-C800; the two EHEIM e300 configurations end at 264 gallons. Finnex's TH-800S remains outside the matcher because its required separate controller and lower-volume condition cannot be fully represented. This is a scope limit for reviewed records, not a claim about every heater on the market.

QPH tank bands: compare the package ceiling without losing the lower edge

Decision: AquaTop’s QPH manual lists 10–15, 20–30, 40–60, 55–100 and 80–130 US gallon bands for QPH-50/100/200/300/400; the exact cartons show conservative upper comparison ceilings of 15/25/55/80/130 gallons, respectively, while the max-only finder cannot enforce any of those positive lower band edges, so all five reviewed QPH configurations remain reference-only rather than active volume matches.

• At 15 gallons, the reviewed QPH-50 remains a reference while the distinct GH PRO 50 W is an active candidate at its own listed 15-gallon ceiling. Check 15 gallons and read GH PRO 50 W.
• At 16 gallons, GH PRO 50 W has left its 15-gallon maximum and EX-100 remains an active candidate; QPH-50 is still reference-only. Check 16 gallons and read EX-100.
• At 25 gallons, the exact QPH-100 package label sets a conservative comparison ceiling, but EX-100 is an active candidate and QPH-100 remains reference-only. Check 25 gallons and read EX-100.
• At 26 gallons, QPH-100 remains a reference above its conservative package ceiling; EX-200 is an active comparator. Check 26 gallons and read EX-200.
• At 55 gallons, GH PRO 200 W reaches its own stated maximum while QPH-200 remains reference-only despite the manual's 60-gallon endpoint and package's 55-gallon label. Check 55 gallons and read GH PRO 200 W.
• At 56 gallons, GH PRO 200 W has left its cap and GH PRO 300 W is active; QPH-200 remains a reference above the package's conservative 55-gallon ceiling. Check 56 gallons and read GH PRO 300 W.
• At 80 gallons, GH PRO 300 W reaches its own cap; QPH-300 remains reference-only despite the official 100-gallon endpoint and carton 80-gallon label. Check 80 gallons and read GH PRO 300 W.
• At 81 gallons, TH-C300 remains active and QPH-300 stays out above its conservative 80-gallon carton comparison ceiling. Check 81 gallons and read TH-C300.
• At 130 gallons, QPH-400's official band and package agree on a 130-gallon top, but QPH-400 remains a reference; TH-C500 matches. Check 130 gallons and read TH-C500.
• At 131 gallons, QPH-400 remains reference-only beyond its upper comparison ceiling and TH-C500 remains active; no QPH model enters the active set. Check 131 gallons and read TH-C500.

At 15 gallons and 16 gallons, compare the active GH PRO 50 W review at its separate 15-gallon ceiling; QPH-50 remains a reference at both values. At 25 gallons and 26 gallons, compare EX-100 at its own 25-gallon ceiling and EX-200 above it; QPH-100 remains a reference. At 55 gallons and 56 gallons, compare GH PRO 200 W at its 55-gallon ceiling and GH PRO 300 W above it; QPH-200 remains a reference. At 80 gallons and 81 gallons, compare GH PRO 300 W at its own 80-gallon ceiling with TH-C300 above it; QPH-300 remains a reference. At 130 gallons and 131 gallons, compare TH-C500 while QPH-400 remains reference-only at either volume. These are same-condition volume-only checks; actual match counts are not a performance result or a guarantee of suitability for a particular room, water depth or livestock.

The official bands and visible package labels disagree at the QPH-100, QPH-200 and QPH-300 upper values; the comparison above uses the lower package figure as a conservative screen while preserving both source claims. The start of each band is a manufacturer-stated lower edge, not a demonstrated safe minimum. See the separate five-size QPH comparison and exact QPH-50, QPH-100, QPH-200, QPH-300 and QPH-400 assessments.