Thanks for your reply! :)
The water is from the tap; it only filters out the chemicals as far as I know. I've been raising fish on it for over a year now. Could it be harming my fish, but not killing them instantly? What would I have to get to add the minerals back in, if that is the issue?
No, I haven't tried any other fish food, except for Hikari at the start but people told me to stop buying it because it wasn't healthy. I have tried the pellets, blood worms and peas. Maybe I will go to the store tomorrow for a new kind. Is there any way to entice him to eat? He seems hungry enough but more like he's not interested. Like he doesn't know it's food.