Seahorse keeping isn't hard, it's easy, if you do it right in the first place.
For a seahorse tank, you are going to want to dedicate it to a pair. 30 gallons really isn't big enough for more fish than that. The sixline is a definite no-no, the perc is iffy, and the firefish are OK, but again, truly not enough room.
Seahorses are messy, way more so than regular fish. They do not have a stomach and require daily feeding, unlike most other fish who can easily go 2-3 days. They are prone to bacterial infections, which are more likely to occur in tanks where the temp goes over or stays above 72 degrees. They require water movement, but not necessarily strong circulation, so dead spots may be an issue. They are quite well known for wrapping their tails around corals that sting, propellers that cut them off, clams that close up on them, etc, so the tank has to be seahorse safe and the corals have to be seahorse friendly.
ALL of what the LFS are getting right now are Vietnamese "tank raised" seahorses...read... raised in the ocean in a net and destined for Oriental medicines if not sold to the aquarium trade. These horses have been exposed to all of the diseases and worms that are available in the ocean. Their "training" to eat frozen is either eat it or die, and they are normally shipped very, very young. While experienced keepers can sometimes overcome some of this, I recommend a first time owner purchase their horses thru a reputable breeder. My highest recommendation would be from Dan Underwood at SeahorseSource.com. I know Mike (mikencarol) has a couple of personal contacts and may be able to help more here.
A happy pair of seahorses can deliver between 200-700 young every 14-19 days. That's not to say it WILL happen, they aren't guppies, but it CAN happen. The babies WILL NOT live in the display tank. If you want to raise them, it requires several other, prepped, cycled, ready to go tanks, some specialized for some species, and yet still more setup for the feed, normally BBS and/or rotifers. Now your pair of seahorses has turned into a 24/7 time consuming hassle.
So, if you can live with a 30g tank with only one pair of expensive horses in it, keep it below 72 degrees year round, allow only those corals, inverts and fish which are compatible, be prepared to feed live daily, as sometimes even frozen "trained" horses refuse to eat, do weekly water changes like clockwork, and be prepared to undertake a huge amount of dedication towards trying to raise the babies, then yup, you should definitely make it a seahorse tank.
I'm not trying to talk you out of seahorses. I absolutely love mine, and they are the reason that I both got into saltwater in the first place, and why I got back into it several years later. I just want you to know some of the ins and outs.
I would be more than happy for you to come over and see my seahorse tank, and to share whatever knowledge I have about them with you. They definitely do require some special preparation, but I think they are so worth it in the long run.
