New Tank, Please Help!!

[wayne]

Matt the first thing you should do is rush out and get hold of a copy of the New Marine Aquarium by Mike Paletta which is an excellent book for novices. I would guess that the reason your fish are breathing hard and dying is ammonia poisoning so you should also get test kits for ammonia and pH at least, plus a hydrometer if you haven't one already and get used to doing regular, likely daily water changes while your tank cycles and stabilises.
You need to learn to research - it's not really very great to go out and buy living creatures and then try to figure out what to do with it afterwards, even if they are 'just damsels'

 

[wastememphis]

star fish are invertabrates, if they get sick there is little you can do to help them. you have to acclimate them to the tank, extremely well... but i have never heard storys of a bad star fish... dont buy one until your tank cycles and you can support the things it will eat in there. research like wayne said.

 

[OrionGirl]

Aside from the cycling issue, do some research on the fish you want. A 30 gallon tank will not be large enough for an adult cowfish.