When I first bought a clown, I noticed he would be gasping in the morning but would quit a couple hours later. I thought he was scared from the light coming on. When I bought my second clown, they both were breathing hard for some time evey morning. I added an air stone and small outside pump to my 10 gallon nano and no gasping fish anymore. I put the airstone in the back compartment because salt would build up around the fans. I thought with waterflow and plants and live rock it was enough oxygen but it isn't.