Sorry, didnt realize you were looking for more help than just "Could it be done".
You dont need a powerhead. A filter is enough flow usually. A strong powerhead will knock them around. My seahorse tank and the one at my LFS both used the overhead pump as the waterflow. (Eclipse in their case, generic eclipse type in mine)
They really cant have ANY fast fish in their tank. They just dont eat fast enough, they tend to stare at their food for a good 30 seconds before eating half the time.
Finally, you CAN put pipefish in with them, and there are some REALLY NICE looking pipe fish out there. I mean UNREAL looking.
Seahorses will wrap onto them and ride em.
In your tank, you can have liverock, but try and get branchy type, and DEFINITELY have a seafan or something similar for them to latch on to at all heights.
I have also seen reef tanks with seahorses, but once again - no fast eating fish.
One thing to think about.. cause it REALLY happened with me. Do you want a seahorse tank to watch?? Or just to have somewhere in the house. I REALLY wanted to do seahorses. I was excited for WEEKS about this tank I had and couldnt wait for the cycle. well, when the tank was ready I RAN out to go get my seahorse. I bought 1 black, and 1 yellow. I brought them home and I put them in.... and..... and.... AND...
Absolutely NOTHING
The thing about them, is they are beautiful creatures, mystical even. But for the most part they latch onto something and well, do nothing. Afterwards I ended up putting a garden eel into it and he was fine with them, and provided a little entertainment from time to time, but ultimately, I gave the seahorse to a collect who has a reef seahorse tank that they take great care of, and I moved on.
I guess what Im saying is, envision yourself with the seahorse tank all set up. Are you imagining sitting there looking into the tank and watching your seahorses do a lot of stuff? If so, dont get it. I have gotten more entertainment out of a Horseshoe crab (damn drunken crabs).
Im really not saying dont try it if you like, just letting you know that they really dont do much worth watching. Especially after a couple weeks of having them. I gave them to my friend because she has a love for them I couldnt find and about 3 months later, I was hitting the point where the competition of my reef tanks was just taking all my attention.
alianated