Goldfish tank not setting in?

I have had many tanks of fish. I would start out with a max of 2 fish. If you add more then that you will over load your tank and the fish will die. Have you added any stress coat or you also can buy bacteria. Bacteria is the most important part because with out it fish will die. You should only do 1/4 water change but it should be done every week. Every time that you do a water change you want to put stress coat in. If you have the filters that you have to change dont change for awhile. If a fish dies get it out right away. I hope these ideas will help.