So I'm the proud owner of two 8 month old marginated tortoises purchased from Chessington Garden Center, I've got the vivarium, books, food and suppliments and they seem very happy, they do tend to climb in their food and get their salad mix balls on their shells and legs, do I need to try and clean them and what with, they also climb in their water bowl which tends to clean the underneath of their shell but not the top, should I be treating their shell with any oil or anything? Bel.x.