Help!! 20 gallon

[rizzamatic]

I have a 20 gallon tank (yeah I know it's kinda small) that I've recently started back up. There is a lot of live rock in the tank, some that has lots of algae--probably because the person I got some of it from didn't take very good care of his tank. I've got a couple of damsels, red and blue leg crabs, 3 snails, lawnmower blenny, and camel shrimp. Every time I try to add a new fish, it'll live for 1-2 weeks, then die. My water tests fine.... I am running a powerhead and a Penguin Bio-wheel 200...and appropriate lighting and heat. Any suggestions for adding a UV Sterilizer and how exactly do they work? Would this be better than a protein skimmer?

 

[bang guy]

A protein Skimmer would be better IMO.
What type of fish are you trying to house with the Damsels? Do you know what species of Damsel you have?

 

[rizzamatic]

I have a Green Chromis and 3-stripe. They really aren't that aggressive. I just lost a Skunkback Pseudo. Before that, I lost a percula clown, and a firefish goby.
You think a protein skimmer?

 

[nomad]

The 3 stripe isn't going to allow any more fish in such a small territory. Whether or not you are seeing it, I just about guarantee the 3 stripe is harrassing the new fish to death.