How should I clean the sponge in my filter?


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Many filter manufacturers recommend that fishkeepers wash their filter sponge under the tap. But this is a very bad idea, as Matt Clarke explains.

The first thing you should do, in most cases, is completely ignore the instructions! Some advise you to wash filter media under the tap, which is a very bad idea.

Most filters work in two main ways: they sieve out fine particles from the water and trap them in a sponge, and they act as a home for ‘friendly’ bacteria that convert toxins produced by the fish and their wastes into less harmful nitrate, which you can remove by doing partial water changes.

These bacteria are essential, but tapwater will kill them, so never wash filter media under the tap. Instead, syphon some tankwater into a bucket and rinse the media in that. This will remove the trapped dirt but won’t destroy the bacteria.

If you’ve got two sponges, clean them on alternate weeks for best results.

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.