I am a fish lover since I was a kid. My stepdad had several aquariums, one of them an 80 gal. He raised oscars, angels, various cichilids. I had my own aquariums in adulthood, biggest being 20 gal. I have raised oscars and angels as well, with success but I am now doubting my expertise or should I say lack thereof. I bought a fishtank a few years ago, it is beautiful, but it is hard because it is in the shape of a huge fishbowl. It is. 13 gal. I have just had five goldfish die from ich. My husband picked a "calm" one from the pet store and it died within four days. I saw the white spots on it and started treating the water with nox-ich. Another three days and the rest died. Now I don't know what to do. The tank is infiltered but I do a 25 percent water change once a week, vacumming the gravel. Should I leave the tank running or do a complete tear down. When should i introduce new fish? Any help would be great!