I do 30% weekly on all of my adult tanks and 25 - 50% MWF on my fry grow outs. I've often wondered if it was really neccessary to do so much but so far our fish have been really healthy so we've kept it up.
A friend of mine had a 30 gallon tank with 2 6" jack dempseys and 1 common pleco.
the tank had been running for 1 year and he had never done a water change just add water when it got low. I told him his parameters were probly through the roof. The only thing is the jacks were breeding. I tested his water and there was not nitrite or ammonia but it had 200ppm nitrates.. So i guess it is possible,
