My friend has a turtle and she is very old, around 35+, and i just noticed while i was over her house that she had a bit of tail missing or something and i tried to tell her but she's like "oh she's just old" but is texting me now that it does look bad. They have had her in the same tank her whole life, only a 10gallon with a few bricks for a basking platform and an aquarium light and a h.o.b filter. She also seems to be overweight as you can see in the pic. I advised for her to get a new tank because her family honestly didn't know how to take care of a turtle and her family just took it from a family member and have had her ever since, but told her not to simply because i was worried that she would get too stressed out and might even die from the change of everything and then only have her for a few more years. She is a musk turtle and here are some pics of the tail damage. Thanks!