According to latest scientific survey, 32,000 species of fish had been described bill date now in 2011. That is more than the combined total of all other vertebrates: mammals, amphibians, reptiles and birds. Fishes are the most numerous vertebrates living on this earth and worldwide there are over 25000 species of fishes. Of this about 48% live in freshwaters that constitute just 0.01% of the earth's water. When dealing with fish diseases, first you have to identify what you're treating. There is no meditation that is effective against everything.