I had 2 Mystery snails. One grew like a weed & had a perfectly shaped spiral but the other one only grew a half inch over a 6 mo. period & it was a bit bumpy. Now I have 3 new snails to replace the others. I feed them zucchini & there is plenty of plants & algea. I want them to have the best shell I can give them. I'm doing everything I've been advised & so far no problems. I just want to make sure I'm doing everything I can to promote hard & healthy shells. Anyone want to weigh in on this for me?