Canister 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 canister filter is a sealed pot that lives below the tank. It pulls water down one hose, pushes it through stacked media baskets and returns it up the other. Everything happens outside the display, so media volume is limited by the cabinet rather than by the tank, which is the whole reason the format exists. What that media does is what the Merck Veterinary Manual describes for any recirculating system. Mechanical stages catch particles, which keeps the water clear and stops waste breaking down in suspension. The biological stage is surface area for two groups of nitrifying bacteria: the first turns ammonia from fish waste into nitrite, and the second turns nitrite into nitrate, which is much less toxic but still needs exporting through water changes. Chemical media is an optional third stage aimed at specific compounds, such as ion-exchange resins or zeolite that binds ammonia. Canisters suit planted tanks because they are closed. Water is not tumbling through air on the way back, so injected CO2 stays where you paid to put it, and the return can be aimed with a spraybar or a lily pipe to move the whole tank without churning the surface. The costs are practical ones. Priming and hose disconnects are a chore, a leak empties onto the floor instead of back into the tank, and the sealed body hides how clogged the mechanical stage has become until flow visibly drops. Rated flow figures are measured on clean, empty units on a bench; once media, hoses and lift height are in the way, real turnover is lower. Treat the manufacturer's number as a ceiling rather than a promise, and size the filter with headroom.

Source

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

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