Erik,
I am certainly no expert, but I do have a seahorse tank. (It's my first attempt, too.) The meeting is at my house this coming weekend, so come on over and see it. It is nowhere near pristine, but it is a work in progress.
I have a couple of erectus seahorses that I bought from Aquadome here in Austin. They have done very well. I could watch them all day and night!
I had a couple that I got for Christmas drop dead. The LFS said they were reidi. However, I strongly suspect they, too were the pen raised ones. They seemed ok for a while (though they were always on the thin side) then suddenly they were gone. I was depressed for days.
I strongly suggest paying a little more up front for the horses and getting them from a trusted breeder. It sure beats buying a cheap horse and spending some mega $$ on medication only to watch them die.
I have heard rave reviews about Seahorse Source and Draco Marine. In fact, I will probably order my next pair from one of them.
Erectus and Reidi are supposed to be some of the hardier horses.
The moment his HEAD is in view, hit it with the LIVE ROCK!