Originally Posted by
bluelagoon
Every few (3-5) weeks is along time to change out 25% WC IMO for pristine water, considering added ferts and waste from plants and fish. During WC's deep siphon the substrate to remove most organics so there's not much nutrients for the nasty things that may cause harm/disease. Try to aim for 10 nitrates with WC's and then ad some ferts if needed. Sometimes it takes a long time (a year or two, other discus right away for water quality issues to effect the health of discus while other species can do well.