I don't think that a copepod population would last long, though. However, there was an article on Advanced Aquarist(?) a while ago about the DIY automatic feeding system some guy had set up for his seahorses. It fed them mysis and involved a mini-fridge, a blow dryer, a rotating shelf-type-thing, and sieves. Sorry I don't remember much more than that! Still, if you have a bit of extra money, you could do that. Also, you might try going on some other forums like seahorse.org and fusedjaw.com to see if there are any seahorse keepers who live near you who might be willing to take care of them. If all else fails, you may be able to hire one of those aquarium maintenance companies to take care of them for the vacation. You would need to leave them detailed instructions on how and when and how many times to do the various maintenance tasks, but I think they would do a good job of it.