I have my seahorses in a 45 gallon tall tank. About 30 pounds of
live rock, live sand, 4 fake plants for them to grasp to, about 20 blue hermits, a scarlet reef hermit, one yellow tail damsel, a serpent starfish, 4 peppermint shrimp, and a pin cushion sea urchin. Only regret I have is the urchin....he knocked a piece of rock off the pyle and it murdered my largest seahorse, crushed him against the glass...he was so cool too.
Anyways, feed 'em mostly vitamin enriched live brine shrimp (keep them in the tank stand in a 5.5 gallon tank with an air driven corner filter, and include every couple of days frozen mysid shrimp (crabs and shrimp love that stuff too).
Everyone leaves everyone alone, the damsel cares nothing about anything but eating and hiding...really reclusive, but hey, he has been around awhile and is kickking good. The shrimp do the shrimp thing and same for the star. That stinking urchin though is going to be relocated into the 90 here before to long. He is brutal on the delicate pyle of rocks I have setup.
Seahorses are cool animals. But before one decides to endure them, one really needs to make a committment to them. They require excellent water conditions and feedings about 2-3 times a day, they dont tend to move to quickly so I turn my main filter off for about 15-20 minutes during feeding, skimmer stays on. They are very entertaining to watch though, some people even get theirs to feed from their hand.