They do tend to be healthier and live longer in temps under 74F. It is possible to keep them under MH's and keep lower temperatures IME. Just move to Oregon and keep the window cracked
There is some evidence that the brighter light will turn a
seahorse a darker color (kind of like a tan but way different when you break it down), but IME this has not been true when using T5's and MH's. It's been some time for me, IMHO if it is true my seahorses would have been black.
Do get your temp down though, it will make your life easier. A well placed fan or Ice Probe unit is probably all your going to need.
HTH
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The deadly and highly trained Marine Firefish, kind of like a Navy Seal, but more macho with Umbra Classification