B&G, I don't know the answer to the nitrate question.---I've not researched it or tested for nitrates. I base my water changes on available time and observations of the fish' behavior.
I don't know how much pumping occasionally will help either since ammonia can rise rather quickly. If you used a sump system with a biowheel, like a tidepool, the bacteria may remain viable. I have a secondary 55g tank that I use to keep hundreds of fry and eggs in before selling and the bio-wheels in it are often dried out when not used, yet when I refill the ank and resart the filter system, the ammonia rarely ever climbs above 1ppm.
