My betta of 5 months is sick, with I suspect fin rot. He is listless and will not eat, and is keeping his fins closed. Yesterday I did a 50% water change, and I've treated him with M2, salt and slimecoat.
My question is, how often should I change water for a sick fish?
What size tank? Have you tested the water using a liquid reagent kit (test strips are useless), you want to test for ammonia, nitrite, and nitrates. Do you have a heater and a filter? Gotta know these things to help you.