I'm amateur hour with seahorses but the majority available seem to be CB. The only wild ones I've ever seen are from Florida (which isn't on the high end of tropical most of the year) and the leafy/weedy from Southern Australia where it is very temperate. Hippocampus barbouri comes from Indo but they get too large for a 20g. The erectus, which you can find CB, come from soundly temperate areas. As an aside - seahorses in South Asia have seen stark population declines from over collecting so your not likely to see wild stock from there.
The seahorse terminology has gotten muddied in recent years. The terms CB (captive bred), TR (tank raised), NP (net penned) and WC (wild caught) is confusing and sometimes misleading.
WC is the most straight forward. It refers to seahorses that live and were born in the ocean but were taken out for the pet trade. Sadly the long term prognosis for these seahorses is very poor. They generally are not fed well between being caught and ending up in a lfs. They were used to eating live food and thus will not eat frozen mysis. Then they are offered live brine shrimp with is barren of nutrition. Thus they are malnourished and weakened. Also they are often kept with other fish and exposed to many pathogens and their lack of immunity allows them to become sick. Finally if the lfs is not knowledgable about their needs, then the customer is likely to be misinformed as well.
Similar to WC is NP. This is generally a practice that poor asian countries do. They encircle a portion of the ocean just off shore that contains a population of seahorses. They may even feed them frozen mysis to get them accustomed to eating some frozen. Then they harvest young seahorses for the pet trade. Unfortunately these young seahorses must endure long shipping. Again they arrive malnourished and often sickly and again their prognosis is poor.
The most misleading terminology of all is TR. Again this is usually a practice done in poor asian countries. Pregnant males are gotten from the ocean and are kept until they have fry. The fry are kept in tanks that have ocean water flowing through them for filtration. These fry are exposed to all the pathogens in the ocean. Because the countries they come from are poor their nutritional needs are not met fully and they are often shipped and sold too young. Once again they arrive at an ill informed lfs malnourished and sickly.
Most WC, NP and TR seahorses do not live past their first year of life.
A true CB seahorse is one that is raised in captivity in synthetic salt water or filtered sea water. They are trained onto frozen mysis as their staple food. The farms or hobbyists who raise them have done so for multple generations and they are adapted for aquarium life. They are not sold until 4-6 months when they are reaching sexual maturity. They are then available directly from the farm or hobbyist and only lfs that are dedicated to meeting their needs acquire CB because they cost more. It is money well spent however because these ponies when sold to an informed hobbyist can live 5-7 years.
That may have been way more than you wanted to know and if you read this whole post, I thank you and so do seahorses.
