tank problem

[jim sawyer]

After 8 years of freshwater, I converted my 55 gal tank to saltwater. Went great for 3 months, slowly adding fish (got up to seven, all small, mostly damsels). After last 2 additions (about 2-3 days)a rust powder like fungus/algae formed all over the tank and in two days the only suvivor was 1 hermit crab. Cleaned and recleaned the tank, and am changing 1/4 water weekly, but the rust reoccurs. I did add 2 damsels as a test and they have survived 3 weeks. Any thoughts for a solution would be appreciated.

 

[kdlbem]

Where are your levels(ammo,ph,nitrites,nitrates)? What type of tank(FO,FOWLR,LS)? What type of filtration do you have running? Did you use tapwater for a water change? Need more info on the tank to start narrowing it down. By the way, welcome to the best board on the net!!! I'm sure the nice people here at the board will be able to help if you provide some specifics about your tank.
HTH, B