Anyone know anything about raising aquatic snails?

I had goldfish and didn't see any snails in the bag, but after a couple of weeks, the two goldfish died. I shut off the filter and air pump and let it set, hoping to get back to it and take it apart in a couple of days. Well, I went to empty out the water and I lost count at 26 baby snails. I turned on the air for them but I don't dare turn on the filter, they are crawling in the filter tube. Any ideas what I should feed them or care for them? I have a local pet store interested in buying them. Any info is appreciated!