That isn't weird. You are supposed to do a routine water change of 15%-25% of water every 2 weeks. That includes using a gravel vaccum to get rid of the excess food/waste. You also need to get a magnetic scrubber to clean the sides of the tanks. You obviously don't need a fish tank if you can't even clean it every 2 weeks. Your fish are in toxic water because the old food and feces.