Not for
h. zosterae. In general, they do fine up to the mid-80's.
For the most part, I recommend no corals in a dwarf tank. They're found primarily in grass beds. Live grasses are great, plastic are fine. Feeding should also include copepods, live mysis (they'll usually eat frozen fine) and the like.
Newly hatched baby brine shrimp (NHBBS) are great for about 4 hours, then they start molting and both get larger and lose egg sac. By 12-24 hours, the yolk is gone and they're basically just crunchy enclosures for whatever the brine are eating. Since they will start to eat copepods, rotifers and even finely crushed flake, having a bit of this in the tank will help them carry it into the sea horses.
Personally, Dan has a great line of options for sea horse feeding and breeding, it's worth the expense to look at it. On the other hand, I don't use them. My
h. zostera come from about a mile away and I'll just grab new grass beds and shake them in a bucket when I want a change of feed.
Jeff