I have used snails in the past. You have to leave plenty of room between frags if you use them though as the snails may knock frags into each other. If you go the scrubbing route you can get more in. All depends on your needs.
well I don't really have room for a rabbit, the thing that worried me about the snails is the fact that I have the first platform raised and if the snails fall it will be difficult to get them out...what about a court jester goby?