How important is to have a air pump and filteration unit in a fish tank ?
A filter of some sort is Vital. Air pump is usually optional. Reason is that all fish produce ammonia, and use oxygen. What a filter does is provide a place for bacteria to live, that break down harmful ammonia into less harmful Nitrate that you can remove with your regular water changes. 1 ppm of ammonia can kill most fish, but once converted to nitrate, 20 ppm is usually safe. Oxygen level relies on the water moving around the tank to exchange oxygen from the air at the surface Normally a filter will move the water around enough to keep the oxygen level up, an air pump and bubble stone just increases that. But it’s an optional extra. There are ways to run a tank without power filters, but they are more complicated, and you have to keep less fish, so you are generally better to just get some sort of filter. For a small tank, an air powered sponge filter will work, and gives you the best of both worlds, biological filtering with the sponge, and water circulation from the bubbles.
