I found out last night that Tuna has Fin Rot. I caught it early and today we bought some Melafix. I was looking for Bettafix but the petshop didn't have it so i bought this. It says it treats Fin Rot open sores and pop eye. I do not have a filter in my tank. Is this ok to use? i plan to change the water in the tank everyday. I have a 1/2 gallon tank about how much do you think i should use? Its says a teaspoon every ten gallons. I need answers quickly! I would like to start treament as soon as possible. Also, if this doesn't work I might get some aquarium salt at Walmart, but i wanted to try this first. Thanks a lot!!!