Hi, I'm new to the forum, but have been using this site since getting my baby RES. He seems pretty happy/healthy, swims, basks, and eats regularly. The problems I've been having have been with the water looking a little oily, algae growing on one of the rocks (how bad is this for turtles?), a dark spot on his shell (like a black dot on part of the scute), and today I woke up to find that half his tail fell off!!!
The tail had looked like it was dividing (cinching in), but I thought that was normal as they grew. It was a bit white where it was cinching in, and it just broke off this morning! there's no blood or anything, and my turtle has the tank to himself, so I doubt it was an injury. Does anyone know why this might have happened? Is this a serious deformation?

