I have something to say about the overfeeding issue. I never knew that show issues could be caused by overfeeding until I caused that problem in my tortoise. I posted a picture of my tortoise because I noticed that in a very short period of time, 4 to 6 weeks, Hershell suddenly and dramatically curled up in the front and the back.I was immediately given many of the comments suggestions, proper lighting proper hydration proper food etc. and was basically told my tortoise had MBD.I do not fault any of the people for saying that because from the information they had it was an extremely logical conclusion. However there were a lot of circumstances that made that not true. After many vet visits and consults from a vet schools the conclusion was that my tortoises bottom shell is outgrowing her top one. I was so confused, I thought I had done everything right, substrate, hydration, calcium etc. And many people here were stumped by it also.Much of this had to do with injuries to the top shell that she had before I got her. But it was accelerated by the fact that I overfed her weeds when they started coming up in the spring. I had read somewhere on this forum, I don't know who said it and it does not matter, that a tortoise could not over eat when they are eating the right food. Wrong. They can if their enclosure is not big enough, she was still in her indoor enclosure 6' x 2' because the weather was not yet warm enough to be outside for any length of time. I put her out side in her well planted, now I realize too well planted, outdoor enclosure for an hour or two at a time once in a while which also contributed to the problem. so the problem was not the wrong food wrong lighting wrong substrate etc. the problem was too much of the good food. I had all the best intentions, the vet had seen her a month before and everything was wonderful but I still screwed up and I will never forgive myself for it.she is healthy, has no MBD or parasites and is doing great but she will always have to deal with difficulties advancing her hind legs because the bottum shell is in the way. If you want that even longer version of the story you can check out my thread on "tortoise dragging his shell" by the way I thought my tortoise was a male I was wrong in so many ways this picture shows the problem the best, it seems to be slightly less pronounced now.No mention of overfeeding? Too much of a good thing can cause problems.
How about the scenario that animals kept outdoors will have their shells worn by the elements.
I personally don't care for animals that have shells that appear to be made of plastic...