I already have the tank – it’s 24" deep, which as Peter said, has proven significantly to reduce of the gas bubble disease. When I actually get around to buying a house, I’ll probably upgrade to something deeper.
The damsels are only going in as ‘canary’ fish – they will be removed before the seahorses are put in. I’ve also put in a little trigger fish and will possibly move my copperband butterfly there for awhile as well, because both in their own rights remove crabs, bristleworms, and other little nasties (esp. the copperband…he likes killing things just for the fun of it). I’m only really concerned by stone crabs and gorilla crabs – most any other crab will only eat fish after they’ve died (hence, they’re the ‘clean-up’ crew). I’ve seen way too many crabs take the blame for killing something that was most likely already dead. After all traces of nasties have been removed, I’ll remove the fish and let the tank sit for a bit to make sure none of the critters that were removed ‘rebound’. I have uncured live rock so I have to be exceptionally careful and wait much longer than ‘cured’ live rock – which doesn’t hamper me at all since I’m moving at the end of August and don’t want to put SH through the stress of the move, so will buy them after the tank’s been moved and set-up for a couple of weeks to maintain levels.
Thanks for the info on the cleaner shrimp – I will probably get a small pair, besides peppermints, and watch them carefully as they grow. If they show any signs of aggression or annoyance to the seahorses they can always be removed to the refugium or my coral reef tank.