Many people don’t realize that there are over 40 different species of seahorses, ranging in size from half an inch to almost a foot in length.
I keep Hippocampus erectus, the lined seahorse, which averages 6-8 inches in length at maturity and tends to be one of the hardier (read: easier to keep) seahorse species. H. erectus can also be bred entirely in captivity, meaning my seahorses don’t reduce or threaten wild populations in any way.
All seahorses belong to the Syngnathid family (as do pipefish and the larger leafy and weedy sea dragons), but the needs and status of the species vary widely–some are endangered, others threatened, and all are difficult to keep in a home aquarium environment. (Note: some species are also illegal to keep in a home aquarium.)
Before bringing seahorses home, it’s wise to research the species’ requirements, including acceptable tank mates (fish, invertebrate, and coral) and make sure you can offer not just an acceptable home but one designed to meet the seahorses’ special needs. Something else to consider: seahorses tend to fall sick and die more quickly when kept with other seahorse species . . . so plan your reef around a single syngnathid species rather than trying to bring different species together if you want to have a long-term relationship with your seahorse pets.