Equipment

I am old enough to have run under-gravel filters when they were just what a filter was. A slotted plastic plate under the gravel, a couple of lift tubes, an air pump chugging away in the corner, and a tank of guppies that outlived the family cat. Then the hobby moved on. Canisters arrived, hang-on-backs got cheap, and somewhere along the way the under-gravel filter went from standard kit to the thing you are gently warned against by every shop assistant and half of YouTube. “Nitrate factory.” “Anaerobic dead zones.” “Antiquated.” I nodded along for years. ...

Filtration is the subject I wish someone had explained to me properly when I started keeping fish, because almost everything printed on filter boxes is marketing and most of what actually matters never gets mentioned. I have run sponge filters, hang-on-backs, internals, canisters and one homemade monstrosity built from a bucket, and the tanks that stayed healthy were never the ones with the most expensive equipment. They were the ones with the most bacterial real estate. That is the whole game. A filter is not a machine that cleans water in any meaningful chemical sense. It is a house for bacteria, with a pump attached. Once you see it that way, every decision about types, media and sizing gets much easier, so that is the frame I will use for this article. ...