This is easy. Keep it natural. That means natural foods that the fish ate in the sea as much as possible. Only feed food with living bacteria in it. (That is the biggest secret) No dry foods. Don't do too many water changes. Add natural bacteria from either soil or better, the sea.
Never use medications or chemicals. After you figure out how to keep your fish healthy using their own immune system, and the tank has a few years on it, "never" quarantine or treat for assumed things.
Build plenty of Natural, tight hiding places where the fish "can not" see you and you can't see them. PVC fittings are not natural and fish hate that and will hate you.
Don't clean up every bit of food or detritus you see. Don't clean the back glass.
Thats my secret.
Never use medications or chemicals. After you figure out how to keep your fish healthy using their own immune system, and the tank has a few years on it, "never" quarantine or treat for assumed things.
Build plenty of Natural, tight hiding places where the fish "can not" see you and you can't see them. PVC fittings are not natural and fish hate that and will hate you.
Don't clean up every bit of food or detritus you see. Don't clean the back glass.
Thats my secret.