I would suggest being extremely careful about what and how much of it you put into the tank. I had one good experience with Methylene Blue: My betta was bulging/bloated and swimming on his side. I added 15-20 drops of Methylene Blue to my 2.5 gallon tank. I should have changed the water much more than I did, but the MthBlu still made his swelling go down and he lived for another 4 months before finally dying. MethBlu is toxic to plants, though, so you will have to remove them to treat him. I would caution you once again to be careful in dosing that you don't use too much.