for the first time in my 7 years I seem to have disease wiping out my fish. I have a reef tank with only 5 fish to begin with but i have lost 3 to ich.( I had bought each of those in the last 6 weeks) One other has a film over its eye and the fifth seems to have either ich or a white film like substance on it. In a reef thank I know there arn't great ways to treat this so Im looking ahead. If i loose my last 2 fish how long should I wait before i introduce fish again. And yes all the testing shows the water is good with no notible changes in ph, salinity temperature or nitrates. This is a 50 gallon tank run with a romora skimmer, no other filtration.