I have a 20gal tank setup and had 2 fancy goldfish. They were fine for about 8 months and then they got sick and died, one at a time. They were lathargic and died. Ammonia, Nitrate and all levels were fine.
After that, I added a heater and did a 75% water change and let it run by itself for 2 weeks with the heater on 84F to kill any illness in the water. I purchased some tetras, 2 pairs of Platys, a Gourami and a pleco. All was fine after a week and half then I noticed one of the Platy's was stressed as the other Platy was harassing him. I saw some Ich. He died. Over the next few days I have been losing 1 - 2 fish a day. Now only 3 tetras and the Gourami are left, but they dont look like they are in good shape. I have done 25% water changes, elevated the temperature to 83F and vacuumed alot of the gravel (There was alot of poop in the corners, where they like to hide). Been treating with Melafix for a while too. I'm assuming they are all going to die, but going forward, what do I need to do...completely breakdown the tank, gravel and all and start over? I cannot figure out what is causing this. Ammonia is 0. Nitrate is under 10ppm. and the pH was a little high at 7.6 before the water changes. Any insight?
After that, I added a heater and did a 75% water change and let it run by itself for 2 weeks with the heater on 84F to kill any illness in the water. I purchased some tetras, 2 pairs of Platys, a Gourami and a pleco. All was fine after a week and half then I noticed one of the Platy's was stressed as the other Platy was harassing him. I saw some Ich. He died. Over the next few days I have been losing 1 - 2 fish a day. Now only 3 tetras and the Gourami are left, but they dont look like they are in good shape. I have done 25% water changes, elevated the temperature to 83F and vacuumed alot of the gravel (There was alot of poop in the corners, where they like to hide). Been treating with Melafix for a while too. I'm assuming they are all going to die, but going forward, what do I need to do...completely breakdown the tank, gravel and all and start over? I cannot figure out what is causing this. Ammonia is 0. Nitrate is under 10ppm. and the pH was a little high at 7.6 before the water changes. Any insight?