My seahorse tank is finally complete and now I am starting a 30

[rayjay]

Yes, he says he has dwarfs and they are H. zosterae. You can fit 3 or 4 on a loonie. Smaller species (pygmy) cannot at this time be kept in captivity, at least by hobbyists and I don't think public aquaria have succeeded long term.
Many species, including H. procerus, are not available to the hobbyist, especially to us here in Canada.
H. fuscus can be kept a pair to a 20g tank but at the moment there are none of those available in the US and I've never seen them in Canada in my 10 plus years of seahorse keeping.
Availability is worse now than some years back when we could get true captive bred from Australia. I used to have H. barbouri and H. angustus that now are not shipped to Canada.
I have now H. zosterae, H. reidi, H. kuda, and H. erectus.
The erectus I imported from seahorsecorral.com about 15 months ago because I couldn't talk any store into bringing them in. Now, Sea U Marine in Markham in Ontario is bringing them in.
I also brought in dwarf H. zosterae at that time.
I didn't know there were any available out west until he posted that he had dwarfs.
There HAVE been successes keeping seahorses in situations not recommended, but the are the exceptions and not the norm. Many seahorses are lost in the attempts to do so.
The successes would have to do much more extreme houskeeping and larger and more frequent water changes to be successful when kept in smaller tanks than recommended.
Unfortunately, people being people, sometimes when everything is going good with no apparent problems, a water change gets skipped here or there, or a housekeeping chore is delayed, and then all of a sudden, a seahorse or seahorses are in trouble, often leading to their demise.
Normally, the water can be problematic and you don't know it because all the hobbyists kits don't test for things like the advancing vibrio type species, or pathogens picked up from tankmates, the two biggest causes of seahorse losses.
Seahorse.org is the most up to date source of information, but a lot of the articles in the library have become outdated so one needs to frequent the forums to really know what is currently known for best chances of success.