How soon do you plan on getting seahorses? I am uncertain about pipefish and temps. If I were you, I'd start to back the temp down a little bit at a time, maybe a degree per week. Watch the corals and see how they do. If you can get them to be ok at 75, then you should be ok with most seahorses that I've seen. BUT, I'm told that the water perameters need to be as perfect as possible for seahorses and that they become lethargic at higher temps.
One person told me that if the water perameters are perfect, they may be able to withstand the stress of higher temps, but only a degree or two higher. My girl is an h. comes seahorse, also called tiger tail. She is not lethargic at all even when the temps reach 77 degrees. My water is maybe not as perfect as it could be. I sometimes have about 20 on the nitrates. But usually it's 10 and negligable or zero readings on everything else. I don't test for phosphates and have no idea how that effects the seahorses. But I'm fighting red slime so I'm sure I have plenty of phosphates.
I'll bet it depends largely on the horeses and where they came from. Like most creatures they can probably adapt. But that would incluse the corals too.
Suzi