I've never heard of H. fisheri being for sale before, and as their confirmed habitation is Hawaii, I can't believe they would allow collection of them.
Suspected distribution includes Australia and France (New Caledonia).
Only common name listed is Fisher's seahorse.
I suspect then that tank conditions should be similar to those needed for other tropical seahorses and that is extremely clean tanks and temperature range of 68° to 74°F to lessen the effects of nasty bacterial that plague seahorses in tanks, especially when temperatures go above 75° as the bacteria seem to multiply exponentially with each rising degree.
NoobtoSalt, if you haven't already read through the links provided at the bottom of "
My Thoughts on Seahorse Keeping", I'd suggest doing so before too long. The links there are written by experienced seahorse keepers and by Dan U, a commercial seahorse breeder.
Any further questions you may have after reading those links can be addressed on the forum here.