I just wanted to jump in as a long time seahorse keeper and clear up some misconceptions. Seahorses, especially captive bred ones (true captive bred, not tank raised seahorses) Are not nearly as difficult as people make them out to be. Are they as easy as clownfish? No. But there are many other aquarium fish that fall under difficult before these guys.
What they are is different. They have different requirements than many saltwater fish, and if someone goes into it thinking that they'll be just like every other fish they've raised, they're not going to have any luck.
I also wanted to jump on the low flow thing. That's old knowledge, and it turned out to be incorrect. Seahorses do quite well with a brisk flow. I keep my seahorses at around a 20x turnover rate. The important thing is to protect them from intakes, give them sheltered areas, and don't have the flow blasting them directly, say a single directional powerhead.
Temperature is also turning out to be pretty critical for seahorses. Seahorses are prone to bacterial infections, and temperature helps speed up the proliferation of bacteria. So most people keep their tropical seahorses in the low 70s, which turns out to work out fine.
I do agree that you should take your time setting up the tank before getting seahorses. I recommend that anyone new to saltwater keeping, plan to wait at least six months before you get seahorses once the tank is set up, so you can get used to how a saltwater fish tank works. Its those first months you'll be the most likely to screw something up. I would add fish before them, just make sure they're seahorse friendly fish (there are many kinds) and make sure the tank is big enough to accommodate the seahorses and tankmates. I would think that a 36 gallon would be fine for a pair and a couple non-seahorse fish.
Also, species matters. Probably the easier to care for are Hippocampus erectus. I don't want to say they're bullet-proof, but they are definitely the most gregarious and least prone to refuse food.
Finally, one thing to keep in mind is that they do have a specialized died and can't go long periods without food. Which means feeding frozen mysis a 2-3 times a day, and making sure that you have a trustworthy petsitter when you go on vacation.
