Agreed completely, in hospital tanks they can be useful. My tanks just have heaps of circulation, and quite a lot of surface agitation, therefore removing the need of an air stone completely.Junne said:Depends on the use.. For example, its often used to aerate the water and provide a bit of oxygen. This is useful if you are trying to cool the tank and or using it when you have to raise the temps up ( for treating ich )
Also some plants thrive better with water movement and to help algae. Circulation and aeration has shown to be effective in controlling algae.
Air stones circulate the water from top to bottom, but gently, helping with gas exchange. Technically, they don't add oxygen to the water. A bit of surface agitation and a powerhead or 2 will get you countless times more oxygen, circulation and gas exchange in your tank than an air stone will.mmp4 said: