Wow Legs

Our little gold fish seems sick. Stays in the bottom of the fish tank a lot. I noticed that since we started the business of having a gold fish and a few variety of fish in our house we had bought about 6 more. 2 varieties every month. Why? Because they died one by one. The root of the problem? Was that I kept on changing the tanks water 2x a week. Meaning we haven't got a filter to do all the cleaning. I thought it wasn't essential (thought it just now huh). Well our fishes were stressed and now I just bought them a filter and they seem relaxed now. Thank goodness for that c: