Hey Youkai -- glad to hear that you've got a survivor

Just keep him eating, and I'm sure he'll do great...
I had the babies set up in a 5 gallon tank, with one of those old fashioned corner filters (the current produced isn't strong at all, so it seemed to work fine with them). I was suctioning crap off the bottom and doing partial water changes every day or 2... and feeding the babies at least twice a day with newly hatched brine.
Beyowulf -- the key to keeping seahorses is to buy them Captive Bred. You get a healthy animal that is usually guaranteed to be eating frozen shrimp (mysis is best). Wild caught animals usually pass away within weeks, or months at the most due to sickness or starvation. Many will refuse to touch frozen food, and sometimes finding live food for them is almost impossible.
Once you've got CB seahorse though, they're really not that difficult to keep, as long as you make sure to maintain quality water conditions for them, and feed them at least once a day.
If you have any other questions, feel free to ask

Seahorses are amazing....