I have a 39 gallon tank. It's been up for around 3 years. I only have 2 of the 8-10 original fish left, Bicolor Dwarf Angel and a Banggai Cardinal. The rest just vanished. I have Yellow Star Polyps and something I just picked up not sure what it is. I do semi regular water changes. I have had different corals that have all died. At that time I was doing weekly changes. Water tests are always good. Not sure what to do.