my system uses well water on a constant flow thru basis,similiar to one described by Bruce condello, i think. so i dont have a filter.But i do have a big aquariun aerator. I do flush the tub out , about 80% of the 150gal. total, on a weekly basis, and they have shown no ill effects.My sense is, these are very hardy fish, not terribly sensitive to water quality.i have noticed they eat a lot more at 70deg. than at 62 deg. or so. So you may want to target the low 60's, if you just want them to maintain their size, and not grow too much.
