Dwarf Sea Horse - Scientific name Hippocampus Zosterae
It may be best if these little guys are in a tank just for them so they do not have to compete for food. I recommend feeding them newly hatched brine shrimp with the Artemia species being the best quality. I would also suggest a tank with a low current and no coral. If they attach to coral it may burn them. Soft Corals (like Gorgonians) are safe.