Nope - I would put them at a 1 or 2, super easy. Once they settled in they produced babies regularly as long as I kept feeding them once a week or so. I ended up with over 40 snails in a 5 gallon tank, from just a few adults. I just dropped in 10 or so MTS every week after water changes.
In the 20 gallon I had them in before that, they absolutely decimated the pond snails I bought them to take care of, so I introduced MTS so they would keep breeding. They laid clutches regularly and the babies were everywhere. Very easy to breed.