I'm sure that my neon tetras have died because of neon tetra disease of which there is supposedly no cure. This is because none of my other fish have died.Question is, how do I reintroduce a new batch of tetras to my aquarium? Will the disease stay in the water after the tetras are gone? Will it eventually filter out? Should I do water excanges? I did two but with the tetras still in the aquarium. There are no tetras left now. Should I do two 30-40% exchanges a week apart? Any help here?