Fish dying, inverts ok

[legendboy]

Video of said tank

http://www.youtube.com/watch?v=v47xrDY3jMc

Running a tunze nano skimmer. Tank is 20x20x9 and a 10g sump

Originally Posted by ponokareefer

I'm thinking this is probably disease. I have seen some nice smaller set ups without skimmers that do fine.
Damsels are territorial, so having 8 damsels in a system will be very stressfull on them except in a large system. I'm guessing one or more of the new ones had a disease that you couldn't see, and the stress of the move and 8 damsels together caused all the fish's immune systems to wear down and then fish died. As others have pointed out, quarantining the new fish would have probably prevented the quick deaths of all the fish.
What types of damsels did you have before, and what kind were the new ones? Are they known to live together peacefully? Most damsels don't live together very well. In a pet store, they may keep a lot together when selling them like clownfish, but when you get them in smaller groups, they tend to kill each other off.