The Seahorse is a fascinating aquarium specimen that is sought after by many hobbyists. There are about 35 known species of them in the wild and all of the species numbers are dwindeling due to commercial fishing and medicinal purposes in the Far East. People use Seahorses as medicine for nearly every common ailment under the sun in the Far East. Because of this practice and because they can be difficult to keep, they are only recommend for the advanced and committed saltwater hobbyist.
In the wild the Seahorse primarily feeds on crustaceans and small shrimp. In the home aquarium this diet can be difficult to maintain. Many that are kept in home aquariums often perish from malnutrition, starvation or fish disease brought on by these triggers. Feed them often with live fish food such as brine shrimp, mysis shrimp and vitamin enriched frozen foods. They are slow eaters that must be fed often, usually 2 to 3 times per day. Since they are slow eaters it is best to keep them in a species only tank so they don't have to compete with the faster swimming fish for the food.

Commercial breeders are having some success with tank raised seahorses. If you can find a tank raised specimens they will probably cost a little more but it will definitely be worth it. Tank raised specimens should readily accept frozen foods and they should be more hardy and less stressed than those collected in the wild.

In summary, it's best to keep Seahorses in a species only tank with very stable water parameters in a fully cycled tank. Provide them with a high quality and varied diet.