I have not added any new fish to this tank since February/March. I did have some fry moved briefly into a newly set up fry tank for a couple of months and then added back to the main tank. Over the last two months, one by one all of the adult platies have become ill. They all end up seeming deformed with a hump back. Some laid on the bottom, some hung around at the top of the tank. All ended up looking so hopelessly pitiful that they were euthanized. One would fall sick, show symptoms and be beyond help. I didn't have any clue as to what this was. The school of neons, the fast growing platy fry, and the bristlenose have shown no signs. Only the adult platies. At first I thought maybe they were just old. As it started in the first trio added to the tank. Then the other platys succumbed. I still didn't think it was contagious as no other fish in the tank have been affected. I saw the signs of fish tb while randomly googling, now I'm worried. What are my options? I have one adult platy, clinging to life, I was going to euthanize her today. As previously no treatment has had any positive effect. I considered looking to see if she had the nodules on her internal organs which would point to tb. I have no other way of testing further. What about the rest of the seemingly healthy tank inhabitants? I'm obviously not going to add any more fish, I keep seeing people recommending euthanizing all fish and sterilizing with bleach. I would HATE to do that. I am scared about tank cleaning now. I have never used gloves. How would I even go about having a fish or tank tested for tb? If I tore the tank down and euthanized and sterilized, I would have to know for sure. We have a toddler that loves to help feed the fish, I'm worried about her getting near the fish tanks now. Could this have spread to my salt water tanks as well?