Your HOB skimmer and filter should be fine, unless they have some kind of mass suction. For power heads, you want to make sure that there is no way the seahorse can hitch onto the intake -- many a seahorse tail has become injured that way.
As far as soft corals are concerned, there are various kinds that you can get.
You may want to get some photosynthetic gorgonians -- there are a few that are relatively easy, like Briareum asbestinum, which can grow rapidly and likes areas of moderate flow, and Eunicea spp. (common names aren't real helpful w/ gorgonians, because the same ones tend to be used over and over again for different genera.) Seahorses will often hitch onto gorgonians, and this can cause the gorgonians to retract their polyps, but I have gorgonians that have become quite use to my seahorse (and citron goby) and only the polyps being touched will retract -- the fish certainly are not affecting the health of my corals (although this may not always be the case.)
Many of the traditional soft corals have fairly muted colors. Some can be fairly aggressive towards other corals -- by either growing rapidly (like Pachyclavularia spp. -- green star polyps) or secreting chemicals that affect other corals (like Sarcophyton spp. -- toadstool corals.) Keyna trees may not be the most beautiful corals in the world, but they are easy to keep and many people's seahorses enjoy hitching to them.
As far as suitable fish tankmates for seahorses... again, that really is a personal choice and depends, somewhat, on the individual fish in question. If anything other than seahorses are going to be in your seahorse tank, it is always a good idea to have someplace where you can put those animals should you need to separate them from your horses. A fish's behavior can suddenly change (or you may witness a behavior you had never seen before...) There are multiple small gobies that I would be comfortable housing with seahorses, some fish that -- although fleet of fin, grow only 2" long, and even larger peaceful fish like mollies converted to full saltwater.
As far as soft corals are concerned, there are various kinds that you can get.
You may want to get some photosynthetic gorgonians -- there are a few that are relatively easy, like Briareum asbestinum, which can grow rapidly and likes areas of moderate flow, and Eunicea spp. (common names aren't real helpful w/ gorgonians, because the same ones tend to be used over and over again for different genera.) Seahorses will often hitch onto gorgonians, and this can cause the gorgonians to retract their polyps, but I have gorgonians that have become quite use to my seahorse (and citron goby) and only the polyps being touched will retract -- the fish certainly are not affecting the health of my corals (although this may not always be the case.)
Many of the traditional soft corals have fairly muted colors. Some can be fairly aggressive towards other corals -- by either growing rapidly (like Pachyclavularia spp. -- green star polyps) or secreting chemicals that affect other corals (like Sarcophyton spp. -- toadstool corals.) Keyna trees may not be the most beautiful corals in the world, but they are easy to keep and many people's seahorses enjoy hitching to them.
As far as suitable fish tankmates for seahorses... again, that really is a personal choice and depends, somewhat, on the individual fish in question. If anything other than seahorses are going to be in your seahorse tank, it is always a good idea to have someplace where you can put those animals should you need to separate them from your horses. A fish's behavior can suddenly change (or you may witness a behavior you had never seen before...) There are multiple small gobies that I would be comfortable housing with seahorses, some fish that -- although fleet of fin, grow only 2" long, and even larger peaceful fish like mollies converted to full saltwater.
