I only know of a few fish that are happy in water or pH of 4 and they are some wild discus. A friend of mine breeds them profesionally, and he said it's a nightmare to keep it at 4.0. Maybe i should tell him to move to canada and collect rainwater....lol

I agree with Brian, i never ran distilled water in my misters. They all got tank water from my 75. I kept a second set of nozzles that got swapped each month, then soaked in vinegar.