I've also heard that puffers need to chew or their teeth will grow long like rodents. But I'm not convinced that is really true in the case of dp's. First of all, has anyone witnessed an actual case of dp with overgrown teeth? I've never heard of it happening. Second, anyone who has ever kept rodents knows that they chew anything and everything that is chewable, and they chew all the time. If dp's needed to chew, why wouldn't they chew your plants, driftwood, and equipment as well? A gerbil would. I think dp's eat snails only because they are molluscivores(sp?) and have a jones for escargot, not because they need to file down their teeth. I may be wrong, but I vaccum up tons of empty, intact (unchewed) snail shells every week. They go for the meat and care less about the shells. I doubt if your puffers will chew on the MTS's until their teeth break, but they may not be able to eat them if they have a trap door. Rams horn or pond snails are definitely better. It helps to keep a population of feeders snails in a separate tank, that way you have a constant supply.