I am maintaining a 115-gallon fish tank with eight Gold Fish for the last 4 years. I recently noticed that airstones inside the biofilter would clog in a matter of weeks or months. Fearing for the safety of my fish I decided to do a thorough cleanup. Once I finished I noticed that I was out of air stones and I was too tired to go shopping.

I use medical grade Hydrogen Peroxide (H₂O₂) for many cleaning applications and I thought of giving it a try. Basically in the presence of contaminants Hydrogen Peroxide breaks down to water and Oxygen, none of which are toxic.

2H2O2 -> 2H20 + O2

I mixed about 5CC of H₂O₂ to a 50ml syringe. Then I connected it to each air stone and treated it with about 5~10 CC of H₂O₂ mixture. Instantly the H₂O₂ broke down foaming (O₂). I used another syringe of water from the fish tank to rinse it just in case the reaction could have formed some toxic out compound.

The clogged air stones are working as good as new ones.