I have had a lot of fish die. Yes my tank is cycled. I have treated for parasites and bacteria. I do not know if it is tb or something else and not all fish would have the bent spine and sunken belly. How can I treat or clean my tank of everything before adding new fish? I do still have 4 glofish danios, a snail and some shrimp. I also want to get rid of my pest snails that have gone crazy so if there is a way to do that as well great. Do I have to completely break it down and clean it all, etc? I have sand so I am willing to toss that and get new. I don't want to buy fish that are going to keep dying and I'm undecided if I want to try and remove the problem whatever it is or just trash the tank. Thank you.