I would HIGHLY recommend obtaining only tank raised seahorses. It seems that many if not most wild caught ones will not take to anything but live food, which leads to great expense and poor nutrition.
In my tank, the companions i have for my four pairs of H. Erectus are:
Firefish
Pyjama Cardinal
Mandarin Goby
Australian Pipefish
The cardinal like to get the first piece of food in the tank, but then lets the seahorses have their fill til they are done.
I think your tank set up is looking great. I would suggest that you worry less about the caves and think about adding more spots to hitch on. Each seahorse is going to have it's own preference about it's favorite hitching spots, apparently based on light, flow, hitching surface, and whats going on in the tank. "Caves" in a seahorse tank are more about having a place to get out of the light and into some shade, rather than making the cave a "house", so If you do have caves big enough for the seahorses to get into, I would recommend adding some type of hitching to the "floor" of these caves, so that when they want to get out of the light, they have a comfortable place to hitch. They spend the majority of their time hitching, so In my opinion (and its only my opinion) making sure there are hitching posts in many different flow/light conidtions is important. Gorgonians work great as hitching spots (and are relatively inexpensive corals) (though I do use some fake Staghorn and Acro types to provide diverse hitching surfaces)
Also, don't count that your seahorses will always be in hiding. In fact, out of my 8 ponies, I only have two that like to "hide". Most of the time at least half, if not most are visible and active, at least during the day (I admit, I dont look at the tank much from 1am - 8am, lol....
You'll find that each seahorse really shows its own personality and preferences, and that's why I recommend initially having lots of different setups in your tank for hitching conditions... Once you have them for a month, you'll know what they're liking and not, and can rearrange accordingly.
Many people also recommend setting up either a natural or artificial feeding station, which the seahorses are easily trained to use. It helps you see how much they are eating, and also allows for an easy chance for visual inspection (for both an alive/dead check, and for spotting signs of disease, etc...). I use an old clam shell piece that I attatched to some rockwork and surrounded with hitching posts.
Also, I suggest rearranging your tank every few months. Even by just moving a piece of coral (real or fake) or a piece or two of live rock, the seahorses seem to become fascinated and immediately take interes in figuring out the new surroundings, flow patterns, etc... It's fantastic to watch.
But again, nice job on the tank. Can't wait to see your ponies when you get them. I think i'll shut up now!
>
>
