Well Slack, if there is one thing I have learned, is that Triggers are possibly the hardiest creatures in the Ocean. They are as hardy as damsal when it comes to poor water quality, they are desease resistant, and just downright tough. A close second in my experience would be eels and big wrasses (I don't know about Wrasps). Puffers are very hardy as well. At least you are not trying to keep Tangs, Angels, and Tusks in your prisons.