Actually, I have found that the royal gramma (Gramma loretto) does great with seahorses. Royal grammas are highly territorial and very quarrelsome amongst themselves, but for all practical intents and purposes, it’s been my experience that they utterly ignore seahorses (and vice versa). They have brilliant colors, a docile disposition towards seahorses, and are deliberate feeders that won’t outcompete the ponies at mealtime. As long as you are willing to limit yourself to just one Royal Gramma and quarantine it before you introduce it to the main tank, I’m quite confident it will make a wonderful addition to your seahorse tank.
Bonus Tip: if you do decide to try a royal gramma, Howard, see if you can obtain a Gro-Lux fluorescent tube to use in your light fixture. Osram Gro-lux bulbs put out wavelengths of light that are concentrated toward the red and violet regions of the spectrum. They are intended to stimulate better plant growth, but have the added affect of greatly enhancing any red or orange or purple colors they illuminate. When bathed in Gro-lux light, bright red or orange seahorses literally glow! And so do Royal Grammas — the magenta coloration of these fishes will all but fluoresce under Grolux lighting. The pinkish-purple end of these bicolor beauties will be instantly suffused with a dazzling hot-pinkish purple glow that the ends abruptly where there yellow half begins. Dazzling!
If you look up Mark’s post on stocking his 170 gallon tank on this forum (titled "new 170 gal reef — which are safe tankmates"), you will find a detailed list of the types of fishes that make suitable tankmates for seahorses and the precautions you have to observe when selecting companions for your seahorses, Howard. It’s on the same page as your post but just a little further down — you can’t miss it.
Best of luck with your new seahorse setup, sir!