I would try a different kind of fish. Goldfish get sick so easy and they poop too much. Tetras are pretty good and danios are dynamite! I started up a tank again in may and they are holding up good. 4 of them died when my daughter knocked over the tank and broke it. The 2 survivors lived in a cup for about 2 weeks until I got the new tank ready. The key is to keep the water clean too many nitrates from fish waste is what kills them. I add fresh water whenever the level gets low and I clean the gravel once a month. What size is your tank?