I just had the same thing with my male festae. It looked like a huge double-headed zit above his eye. I dosed the tank with aquarium salt, but saw no change. I took him out of the tank and with a Q-tip dunked in hydrogen peroxide I gently drained the zit and wiped away the pus. I made sure that there was no more pus inside by using several Q-tips dunked in hydrogen peroxide. You have to be very gentle as the tissue is very raw. Be sure not to open up the top layer of skin. just massage with Q-tip until pus oozes out. Anyway, I put him back in the tank and a couple days later the abscess was healing up. After about 5 days, you can barely tell where it was. He's good as new.
