Okay so my freshwater aquarium has gone very very very cloudy. The tank is a few years old but we decided to start using it again. So we bought some gravel, cleaned it off with cold water, and put it in the bottom of the tank, which is 20 gallons. The same day, we filled the tank with tapwater. The coal filter seemed to be running okay and the thermostat was set to 76 degrees. About 3 days later, we purchased 8 fish: 3 rainbow sharks, 3 angel fish, 2 algae eaters. We put the bag in the tank so the fish could adjust to the temperature. After releasing them from the bag, we fed them some flakes, which I believe was the problem. None of the fish ate any of the flakes, so the flakes just floated down to the gravel. A few hours later, the water was really cloudy and the fish were at the top of the tank gasping for air it looked like. I checked the temperature, pH levels, nitrate levels, nitrite levels, and ammonia levels (they were all perfect). Within an hour or so, 2 algae eaters and 2 angel fish were dead. We did a 20% water change but that didnt seem to help The next day(today), the remaining 4 fish seemed fine. They were moving around the whole tank, not just the top, but the water is still super cloudy. I have no idea what to do. I can post a picture if needed... I haven't fed the fish since lastnight, and I dont want them to die... What can I do??? Any advice would be great. Sorry the description is so long...