I agree that is too hot. Check on the type you are planning on keeping to find out their ideal temperature. I keep Erectus at 74 degrees, and I chose them partially because they're able to be kept at higher temperatures than other types.
Yes, seahorses are dirty creatures! They're not clean eaters. Mine are picky and snick their food, and blow part of it back out. Unlike the fish in my reef tank that eat everything that comes near them, seahorses are slower eaters and won't really chase food if it blows past them too quickly.