Sorry about the AOL thing. They reported as as spammers because we sent people email notifications to threads, when they had asked for them. Got us suspended from a server, had to move, just to hard to deal with.
You don't need a sump, but you want one. Sumps are cool. All fo the cool kids are doing it.

There a great place to hide equipment, and you can turn it in to a sump/refugium. Even more benefits when you add the contribution of macro algaes.
Filters are cool I've used them in the past. Cannisters are my favorite, especailly when used as a precursor to a UV. That whole topic depends on how much you want to spend. You can go the sump, refugium, cannister, UV route and the tank will run awesome, or you can do a smaller tank with a hob filter and rely a bit more on the liverock for biological filtration and that will be O.K. to, just a bit more work.
IME I like the cannister UV refugium sump setup the best, but tht's JMO.
A seahorse was my first fish I did not win with a ping pong ball at a carnival. I still have my WC reidi, it's been over 5 years.
IME most LFS don't know much about seahorses, so ask here if you like, or if you decide to get a free yahoo account you can post on seahorse.org and ask there. My SN there is Kevin.

You could always wait until we finish the book, but that could be another couple months until it gets through editing. We are joking by the time we release it we will have already updated new info. Just the way it goes.
Would be glad to help you with your setup. I also know a few breeders on your side of the pond when your looking to get your aquacultered horses. Don't fall for those maricultureds at TMC (IMO)
I don't check in this forum to often but I'm around a bit. Can always shoot a PM as well.