We set our tank up on 11/23/02 and have been adding 3-4 fish, usually tetras, approx. every 2 weeks. We have the water tested frequently, follow all feeding and cleaning guidelines and 1 or 2 fish die or get ich every time we get new ones. I treat with nox-ich as directed but it comes back after treatment. We currently have 11 tetras, one angel and one pleco. Is it standard that one dies now and then or am I killing them somehow? Please advise!