Be sure to find out the species and where they are from. Many seahorses come in overseas and are raised in giant concrete pens with seawater, with all the same pathogens that wild seahorses have. That is the kind of trouble you don't want. They might be "tank raised" not captive bred, which means that the male was harvested from the wild pregnant.
If it is in Hippocampus erectus (that sounds close to what you suggested) then its likely raised in the states, which means most likely captive bred. But $50 seems really inexpensive for captive bred from a fish store. Not impossibly so, however I'd be more inclined to believe they're wild caught. Catherine is right - Color, unfortunately, is completely variable in seahorse species, and wouldn't be a indicator of what they were.
One small point of contention with the above information. No seahorse species is illegal to sell in the US, wild caught or captive bred. However their trade entering the country is restricted by the exporting country - they have to be able to prove the harvest of those seahorses is sustainable and that they are over a certain size. This is why you can still get wild caught seahorses, even if they aren't as common anymore. But you shouldn't, they're damn near impossible to keep, die at the drop of a had, and are really expensive to feed. And that's ignoring all the ethical implications.
Most LPS corals are unsuitable for a seahorse tank because they have stinging tentacles. Seahorses have delicate skin covering their boney armor that is easily stung. This can lead to infection, and seahorses are especially vulnerable to bacterial infections.
25x turnover is not too much for seahorses, especially if you create sheltered areas. I have a pair of H. fuscus in a 15h with 30x turnover. I wouldn't go any higher than that, but slow flow generally means slower than the insane flow that sps tanks have. The biggest concern in higher flow tanks is making sure overflows and intakes are protected. But, as stated, LPS aren't great with seahorses so its probably not a bad idea to forgo them.