Aloe vera, mine have eaten a lot of it. They don't show any negative reaction that I can tell, and it and many other succulents/sedums seem to be will liked by them. "Though this is listed by some as being a toxic plant, wild tortoises in South Africa seek it out and eat it with much enthusiasm", R.and J. Fife, Leopard tortoises, 2006. Moderation in all things? Vic H.