Hey guys, My short neck turtle has started to get this dark black spot on his shell which is soft to touch and underneath it's soft too with spots on it. We have him in a 2ft tank with a dry dock and 10.0 UVB bulb. We run the tank at 24 degrees C and he has calgrit and aquarium sand on the bottom. His diet includes live plants, fish (the occasional that he catches) aquatic turtle juvenile floating pellets. We take him out of his tank a couple of times a week in the sun, if not just out to dry for at least 10-15 minutes. His light goes on in the morning and off at night. We haven't tested the water as such, never had a problem with it since day 1 (we are on rainwater). We don't lose any fish unless the turtle eats them, our fish even breed in this water. Please help my little guy! Cheers.