NICREW Aquarium Internal Filter Submersible for 20-40 Gallon, 185 GPH Review (2026)

Who this filter fits

This filter suits owners of 20 to 40 gallon freshwater or saltwater tanks who want a straightforward submersible filter without the cost or footprint of a canister, and who are fine keeping the unit inside the tank rather than hanging equipment on the back. Its 185 GPH output and 10 watt draw put it solidly in the mid-size range, enough to keep a long 20 gallon or standard 40 gallon breeder circulating well without the flow being so strong it blasts smaller fish or shrimp around. Anyone who wants a spare or backup filter to keep on hand for quarantine or hospital tanks also benefits from its low price point relative to name brand canister filters.

What 185 GPH and 10 watts get you

The filter combines biological and chemical filtration, using activated carbon paired with fine filter foam to trap debris and fish waste while also absorbing odors from the water column. It generates a steady stream of air bubbles alongside its water flow, which helps with oxygen exchange and surface agitation in tanks that do not already have a separate air pump running. An adjustable air regulator lets owners dial back the water flow to a gentler stream, which the manufacturer positions as useful for tanks holding delicate fish or shrimp that could otherwise get pushed around by a filter running at full output.

Setup, flow adjustment and daily upkeep

The filter is fully submersible and anchors to the glass with four suction cups, which is enough to keep a filter this size steady against normal water movement once positioned. Because the flow is adjustable at the regulator, owners can start at a lower setting when cycling a new tank with fry or shrimp, then open it up as the tank matures or bioload increases. Day to day maintenance means periodically rinsing the carbon and foam stages in tank water to keep flow from dropping off, which is typical for any internal filter using replaceable media rather than a self-cleaning design.

Trade-offs against other internal filters

In the site's internal filter guide this model ranks fourth of seven, behind two smaller NICREW and Pawfly filters sized for 5 to 10 gallon tanks and an AQQA filter rated for 20 to 52 gallons at a similar 158 GPH, but ahead of two larger AQQA filters built for 50 to 100 gallon tanks. Against the similarly sized AQQA option, this NICREW filter's main disadvantage is a bulkier housing that is harder to disguise behind plants or hardscape in a scaped layout, and its budget plastic construction can develop a rattle over time if the suction cups start to loosen their grip on the glass.

Verdict and who should look elsewhere

For a 20 to 40 gallon tank that needs reliable mid-range filtration without spending canister filter money, this NICREW model delivers solid flow, adjustable output and basic biological and chemical media in one submersible unit, earning our score of 7.6 out of 10. Aquascapers building a tightly planted display where every piece of visible equipment matters may prefer a smaller, more discreet filter or a hidden filtration setup like an all-in-one tank instead. Owners running a much larger tank should look at the higher GPH AQQA options in the same guide rather than stacking multiple units of this size.

Frequently asked questions