This is my first tank. My sister got 4 gold fish from a state fair and didn't want them, I didn't want the fish just dumped or flushed so I took them. I bought a 10 gallon tank and the girl at petco convinced me to get some more fish. Me not knowing anything about fish thought ok sounds great. So now I have 4 gold fish, 2 pleco, 1 spotted, 1 guppie, and 1 angel fish. I know I have too many for the tank and I really need to get a 30 gallon but for now it's my 10 gallon. I'm doing 50% water changes every other day and I completely change the water once a week. I treat the water and I have a sponge filter that came with my tank, I'm not sure if it's enough the sponge gets dirty quick and I have to change it often like twice a week. Any tips would be amazing please and thank you. I now know I need a heater.