I also have trouble with the snails getting stuck on their backs. I don't know how long it takes them to die when they get stuck, but I often notice them stuck and save them but many times I am too late. They seem to have trouble transistioning from the glass to sand bed.
On the positive side I've had good luck with the large Mexican turbo snails. These snails are quite large, some as big as a golf ball and they rarely get stuck on their backs. They do good job of eating the algae too. They literally leave a path were they ate the algae. These and the emerald crabs seem to do the best in my aquarium of removing (eating) algae. However, I have seen the emerald eat some my green star polyps, which I was dispointed in but it does such a good job of eating hair algae I don't want to remove it.
Good luck with the sea horses. I've heard that the tank raised sea horses are easier then those caught out of the ocean.
