Answers (1)
I have friends with aquaria and they always say it's much harder to keep a salt or brackish tank (which is why most tropical fish are river fish). It's not impossible, though. Although if you're going to keep a salt water tank, keeping sea horses adds various levels of complexity and cost.
I personally love seahorses but I wouldn't consider keeping them without a fair few years aquarium experience. Plus there is the cost. You can only buy them from domestic breeders (no imports) and they cost a fortune to transport (you can be looking at £80/$120US per seahorse including buying them). Plus they are delicate and fussy. You'll need all kinds of equipment to maintain them and you can't leave them alone for very long. It's tempting, though, isn't it? They're so amazing.
This isn't really my area beyond the advice I offered above (which is about as much as I know on salt water fish-keeping garnered from two friends who are experienced aquarists and enjoy talking about it) but I rang one of them for you. He says clownfish are easier and a good way to get into salt water aquaria. He also suggested going for fish that are bred in tanks as opposed to wild fish. He had a whole load of reasons but what I took from it is that fish bred in a tank are better adapted to living in a tank.
What about something simple like a clownfish or two with an anemone, And maybe a starfish?