I would not recommend keeping seahorses in one of the JBJ or Oceanic cubes. I would look for a 40g breeder or something that size and drill it yourself to have a sump. I have to run a HOB skimmer on my JBJ 28g and had to take the lid off to keep the temp at 75 degrees. It's a major eyesore compared to my 75g since it now looks like Frankencube. Plus the in sump skimmers are better that HOB skimmers.
As far as the my tank, I run chaeto in the fuge section of the JBJ and feather caulerpa in the display section. Mine seem to love to teather to the vines and spend a good part of the day there or around the larger branches of the Kenya tree. I have a few acros, gorgonias, Kenya tree, xenia, and zoas. As far as tank mates...a yellow headed sleeper goby, scooter blenny, and CUC. I feed frozen mysis once a day. I havent had any luck with "feeding stantions". The goby usually out competes for food, but after he gets full the seahorse can eat. I use a kent sea squirt to target feed around him. It takes about 5 min, but ensures feeding. I have a small population of pods, but I think between the blenny and the pony this is as much as I'll get.
I absolutely love seahorses, but before you set up a tank, know that they have to eat 1-2 times a day. Mine is now a fat healthy adult, but we never leave the house for more than 1 day. I'm too paranoid to go away for longer than that. I would recommend seeing them eat before buying them.