There are both freshwater and saltwater ghost shrimp. Unless you live in Florida where they are farm raised the saltwater shrimp are expensive due to shipping costs. I used to use Livebrineshrimp.com to buy them in bulk and store them in a 20 gallon designated tank for my dwarf zebra lionfish that refuses to eat anything dead. I subsequently started buying freshwater ghost shrimp from a local fish store
that I gut feed (ie., given high quality food) and have saved a lot of money without any noticeable change in Vlad the Inhaler's health. He's been going strong for over two years on his modified diet.