Hi, I purchased two true percula clowns from my LFS and put them in quarantine for three weeks using Seachem's Paraguard for preventative treatment. I was using cycled tank water from my other tank. Both clowns were eating and doing great. In the meantime I began a new 29G reef aquarium. I purchased 30lbs of live sand and 30lbs of dry rock. After the clowns were done with quarantine I added Dr. Tim's One & Only 12 hours before adding the new clowns and things were great. The clowns were very active and eating well. After 48 hours I turned on the protein skimmer and everything remained well in the tank. I came home today from work and one of the clown was on the bottom of the tank breathing heavily. I immediately took him out and put him back in the quarantine tank...he died one hour later. I have no idea what happened. Since the new tank is still cycling with Dr. Tim's the ammonia level has been around .50ppm. So far the other clown is still doing okay (knock on wood).