OASE HeatUp 300 US Aquarium Heater review

The OASE HeatUp 300 is a 300 W adjustable aquarium heater rated by its U.S. product table for 300 L and by the US product-page copy for aquariums up to 80 gallons. SKU 33805 has a 23 mm diameter and a listed length of 370 mm, or about 14.6 inches. Three hundred litres converts to about 79.3 U.S. gallons, so the matching record uses 79.3 gallons as the lower, conservative maximum rather than rounding above the technical-table capacity. This is an evidence-led assessment of the exact wattage variant; it does not report a physical trial or guarantee a tank temperature.

The 300 W choice is longer than its 200 W neighbor

The body extends to 370 mm, 55 mm longer than the 200 W and 150 W models. That difference may affect whether it can be placed vertically within a particular waterline, so check real interior dimensions, minimum immersion and access before deciding on the largest wattage that seems to fit. Capacity is a ceiling, not an estimate of warm-up time. Room temperature, aquarium cover, circulation and actual water volume all affect heating needs, and the maker’s page does not turn those inputs into a room-specific sizing guarantee.

OASE lists adjustable control from 66°F through 90°F, freshwater and saltwater compatibility, bimetal regulation, an active-heating indicator, thermal shutoff, quartz glass, an included suction-cup holder and a three-year warranty. It names both FiltoSmart 300 and BioMaster 600 for heater/filter integration. For FiltoSmart 300, OASE specifies a separate ThermoFit FiltoSmart 300 (model 48567), not included. The external-filter plan used here is the BioMaster 600 route; a FiltoSmart 300 setup is a distinct arrangement and needs that adapter.

Control claims have boundaries

The secondary adjustment is described as ±2°F in the U.S. feature summary and ±3°C in other product copy. These are two descriptions of calibration adjustment, not documented accuracy or the range of the heating dial. OASE does not state an exact setpoint step in the available product evidence. The light reports active heating, not water temperature. Use a separate thermometer and a credible livestock-care reference before concluding that the actual aquarium is at an appropriate target.

OASE calls the tube quartz glass and claims it can withstand at least twice the temperature of ordinary glass. That does not establish shatterproof construction or impact resistance. A thermal shutoff switch is described, but the exact source does not set out dry-run sensing or a trigger condition. Follow the exact included instructions for placement and operation, especially in a canister-filter installation; neither the broad phrase “filter integration” nor an illustration establishes that an arbitrary filter connection is safe.

Resolve the US voltage copy before plugging in

The exact 33805 technical table states 115 V / 50–60 Hz, but the narrative paragraph on the U.S.-oriented product page says 230 V. That mismatch is significant. This library treats the exact specification table as the best evidence for the catalogue’s US configuration and uses 115 V for matching, but a potential buyer must inspect the physical label. Do not energize a unit on U.S. mains if its carton or device says 230 V; seek confirmation from the seller or OASE. This does not certify any specific offer, stock status or package in circulation.

When the 300 W model deserves a comparison

Compare this model when actual tank volume is no more than the conservative 79.3-gallon limit, an adjustable 66–90°F scale fits the independently selected target, and a 14.6-inch tube can be installed as directed. For an external route, the exact BioMaster 600 named by OASE is the chosen operating plan. If the filter is a FiltoSmart 300 instead, check the distinct ThermoFit 48567 accessory and instructions; the adapter is not included. A tank between the conservative 79.3-gallon boundary and the 80-gallon marketing endpoint is excluded from this match because the source values do not reconcile perfectly.

The scale, power and stated capacity make the model distinct from the 200 W version, while length and integrated-filter compatibility change as well. Those details should not be copied across an entire family. A match only signals that recorded model facts do not exclude a requested setup. It cannot guarantee heat performance, room-to-water compensation, a suitable livestock target, or fit to a filter that OASE has not named.

Questions to settle before choosing

• Does measured aquarium volume stay at or below 79.3 U.S. gallons after converting the technical 300 L maximum?
• Is a roughly 14.6-inch heater physically suitable, and is the planned external installation the named BioMaster 600 or the separate FiltoSmart 300 plus ThermoFit 48567 setup?
• Does the physical SKU 33805 nameplate show 115 V, and is ordinary quartz glass acceptable without a shatterproof guarantee?