It's a stupid idea. Seahorses are not technically hard to keep alive as they don't require super pristine water. However they are very , very slow, fussy about what they eat, and need to feed a lot. Try to keep them with clowns - the clowns will steal their food, likewise 99% of other fish. Kep them iwth anemonaes , and they usually end up in the anemonae, keep them with corals, and they often get stung by the coral. You think seahorses live in reefs in the wild - you think wrong, they live in seagrass area in my (limited ) experience.
Keep them lionfish, they end up eaten, don't kid yourself