I have H. reidi, H. erectus, H. barbouri, H. angustus, and had H. comes but have recently lost both of them.
Minimum recommended size for a pair of seahorses is 29g with each additional pair needing an additional 15g.
Best place to buy seahorses would be from other seahorse hobbyists and from seahorsesource.com and seahorsecorral.com.
Almost all other seahorses found in the LFS's are tank raised or net pen raised, with still the occasional wild caught being found, but all of these come from systems where ocean water is used without treating for pathogens that wildcaught have so they too have the same problems and poor track record of keeping that the wild caught have.
I have a page on my website about my experiences and thoughts that contains links to pages that I believe to be extremely informative to new seahorse keepers. MY THOUGHTS ON SEAHORSEKEEPING
Buying from your LFS is not a good idea. Almost ALL seahorses sold at LFSs are net pen or tank raised.
While they are cheaper than true captive bred, their survival rate is MUCH lower due to the fact they have been raised in ocean water with insufficient filtration and treatment to stop the infestation of pathogens from the ocean water, just like wild caught ones have.
As such, these horses should be dewormed the same as wildcaught ones need by a nine week, 3 stage deworming protocol in which some horses are lost in the process.
Buying true captive bred does not guarantee success but the odds of success are much greater and they are worth the extra dollars to buy.
Other than buying from hobbyists who raise their fry, the next best to to buy from are: http://www.seahorsesource.com http://seahorsecorral.com