Hang-on-back filter

Performance & sizing

Core numbers for matching this unit to your tank and electrical plan.

Power

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Flow rate

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Noise

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Dimensions

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Price range

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Tank fit (L)

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Consumables & maintenance

Rinse mechanical media on a regular schedule; replace biomedia and cartridges per the manufacturer (often many months apart).

Description

A hang-on-back filter clips over the rim, lifts water up a short intake tube with an impeller and lets it fall back into the tank across a spillway. It is the cheapest way to put real filtration on a tank without plumbing anything, which is why it stays the default in fry, quarantine and shrimp tanks. The mechanics are the same as any recirculating system. The Merck Veterinary Manual sets out the three jobs: mechanical filtration to strip particles, biological filtration where two sets of nitrifying bacteria convert ammonia to nitrite and then nitrite to nitrate, and optional chemical media for specific compounds. In a hang-on-back unit all three usually live in one small cartridge or a pair of media slots, and that is where the format's weakness shows. Cartridges are consumables by design, so throwing one away throws away the bacterial colony growing on it. If your filter takes them, swap only part of the media at a time, or repack the housing with sponge and biomedia you can rinse in tank water and put back. Two habits are worth learning. The return cascade agitates the surface and speeds gas exchange, which helps oxygen in a crowded tank and works against you if you are injecting CO2 into a planted one. And because the intake hangs at a fixed depth, evaporation eventually drops the water below the pump, so the filter runs dry, gets loud and can burn out its impeller on the week you forget to top up. Both problems are cheap to manage once you know they are coming.

Source

• merckvetmanual.com — https://www.merckvetmanual.com/exotic-and-laboratory-animals/aquaculture/production-methods-in-aquaculture

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