Jim,
I've put those ghost shrimp in too. For the exact purpose of food. I've used them in my fish mush as well. You can get netfulls with a flashlight at nite right in Eel Pond. I also harvest that macro that everyone calls "lettuce" or "tang something" or other. My tang does like it.
But I'd still venture to guess, that whatever you put in from the N. Atlantic, it'd not make it in the long run. I remember seeing some red snails for sale that were from cold water. I think Calfo's book has a picture of them too. They don't last long in warmer systems.
Cold water systems can be cool though. Especially if you live close to the ocean and have an endless supply of water!