hmmmm seems to me that either you did not acclimate the fish correctly, or something you have added to your system, makeupwater, or other is not right, or your system is just not fully cycled and you went too many additons too fast. hard to say. in order to pin it down you would need to provide all of the information I noted above. If I can be of any further help i will need more information on the system, its setup, equipment, processes used for water changing, mixing up salt, top off and a list, amount and how often anything is added to the system. so I would refer you to the saltwater articles section. there are some articles there that might give you more insite into the marine system to help you identify your concerns. anyway with more information i would be willing to help, but, at this point not enough information to determine why you lost all 5 fish except to say 5 damsels is too many at any time, tank is not yet fully cycled. you will need to establish your sand bed before adding any amount of fish bioload. get your worms, copepods, etc started, and go in with a sand stirrer, cleanup crew 1st when there is enough food source for them (algae). hope this all helps a bit. i know its not a definitive answer to your question but just dont have enough information. Join us on live chat at 9PM eastern time. mon, wens, fri. or anyother time you can catch us there. I could discuss with you there if you like. talk to ya soon and good luck with your system