I have had a 55 gal reef set-up since Dec 2001. I took my time and waited 30+ days before I put any livestock in it. Up until a month ago every thing was fine, now however it seem I can not keep a fish a live in it for anything longer then 7 days. All my corals and invert are doing great, water test are fine, and water changes do not help. I lost 4 fish inside a 2 day peroid anout a month ago, fish that had been it the tank since late Jan. I waited 2 week after this die off and place two new fish in now they are both dead. Any body got any ideas what might cause this??!