OASE HeatUp 100 US Aquarium Heater review

The OASE HeatUp 100 is a 100 W adjustable quartz-glass heater with a 23 mm diameter and 245 mm (about 9.6 inches) listed height. SKU 33802 is the middle step between the short 25/50 W heaters and the longer 150 W body. OASE’s U.S. product evidence states a 100 L capacity and also advertises up to 30 U.S. gallons. Since 100 L is about 26.4 U.S. gallons, this review uses 26.4 gallons as the conservative ceiling rather than treating the larger rounded gallon figure as exact. This is source-led editorial analysis, not an independent performance test.

Size and capacity are specific to this model

The 100 W heater is 40 mm taller than the 25/50 W tubes, so tank height and minimum immersion clearance are worth checking before purchase. The 26.4-gallon conservative limit is not a lower bound: OASE’s table gives a maximum and does not state a minimum aquarium size. Nor is it a prediction of how quickly the unit raises temperature. Heat demand depends on the room-to-water difference, cover, circulation and other conditions, which the maker’s maximum label cannot capture by itself. Measure the water volume rather than using the tank’s outside dimensions or nominal marketing size.

OASE lists fresh and saltwater use, a 66–90°F adjustable scale, bimetal control, an indicator for active heating, thermal shutoff, quartz glass and an included tank holder. The product page also describes integration options: BioPlus 100, FiltoSmart 100, and the BioMaster family in the broader line. For an external-filter route, the exact page names FiltoSmart 100 and requires ThermoFit FiltoSmart 100, model 48507, which is not included. That filter and adapter are essential parts of the external arrangement; a HeatUp 100 alone does not satisfy that plan.

Do not confuse calibration with accuracy

The US-oriented feature block states 66–90°F and a secondary control adjustment described as ±2°F. The same OASE family pages also phrase that calibration range as ±3°C. That calibration adjustment does not establish thermostat accuracy, and the source does not specify a selectable one-degree step. The lamp reflects heating activity, not a measured temperature display. If the keeper needs actual water-temperature information, a separate aquarium thermometer is the relevant check, and the target must be chosen for the livestock rather than inferred from the heater scale.

The product is described as a quartz-glass tube capable of withstanding at least double the temperature of standard glass. OASE does not call it shatterproof or supply an impact test in the reviewed material. A thermal shutoff switch is documented; separate dry-run protection and its trigger conditions are not. Do not stretch those claims into broader safety promises.

Check the electrical edition on the label

The exact technical table for SKU 33802 says 115 V at 50–60 Hz, while the narrative paragraph on the same US product pages says 230 V. The U.S. selector and table support screening the US-listed configuration as 115 V, but the copy conflict is material. Inspect the carton and heater nameplate before energizing it. If the physical item says 230 V, do not use it on a U.S. supply; ask the seller or OASE to identify the unit. The manufacturer’s current site and dealer links do not guarantee stock at any particular retailer.

Which buyer should compare this version?

The HeatUp 100 is a candidate when the aquarium fits within the conservative 26.4-gallon ceiling, the adjustable range suits a separately chosen target, and a roughly 9.6-inch in-tank heater fits the aquarium. For external filtration, consider it only when the complete FiltoSmart 100 and ThermoFit 48507 arrangement is already part of the plan. OASE’s BioPlus 100 integration is an internal-filter option, not equivalent to an external-filter connection. The heater is not described as shatterproof, and exact dry-run behavior remains unknown in the reviewed evidence.

At its 100 L rating, the rounded 30-gallon headline could leave an aquarium several gallons beyond the litre-derived threshold. This guide intentionally applies the lower number to avoid inflating a matching boundary. A valid library match only indicates that the manufacturer-supported conditions recorded here do not exclude it; it cannot establish that the aquarium will hold a desired temperature or that the chosen target suits its inhabitants.

Questions to settle before choosing

• Does measured aquarium volume stay at or below 26.4 U.S. gallons, using the lower of the 100 L conversion and the stated 30-gallon maximum?
• Will a 9.6-inch tube fit with the required water depth and circulation, or is the exact FiltoSmart 100 plus ThermoFit 48507 route intended?
• Has the physical SKU 33802 unit been confirmed as 115 V, and is the buyer comfortable with quartz glass that OASE does not describe as shatterproof?