Water source: RO/DI (reverse osmosis / distilled). You can get this at your petstore, or better yet, at walmart, your grocery store, or lots of times pharmacies and gas stations. Basically, find "drinking water" that has been treated using reverse osmosis and distillation. I use my tap, but I have good tap for saltwater so all I have to add is Amquel Plus to remove the chloramine.
Getting some good live rock is so nice. Really, try posting on your local board at
www.craigslist.com under "items wanted", and also on your local saltwater board if you've found it. That way the LR has already been cured and established in another aquarium so it is full of life and ready to go, and usually cheaper than your LFS. Don't bother getting cured if it has to be shipped, b/c there will still be die off. But, I would search the internet for sites selling pre-cured rock (uncured will make your aquarium room really stink). Off the top of my head, I'd try liveaquaria.com and floridapets.com, but try google and see what you come up with.
Look up "feeding station" on seahorse.org. That will save you from doing a bare bottom or having seahorse food floating around rotting in your aquarium. You put a cup shaped fake coral, shell, reptile bowl, petri dish, etc. somewhere in your aquarium. Then when it is time to feed, you turn off or turn down your filter and/or powerheads, drop the food in the using rigid clear tubing, wait for them to eat it, and then remove the uneaten portion with a turkey baster. You do have to train them to the feeding station.