Hey guys, I was cleaning the red tail's enclosure earlier today, and saw clumps of hard, black, gritty stuff in the urates. Like large sand grains. At first I panicked and thought they were mites but they are super hard and maybe a bit larger than mites. ??? What is it? Any ideas? He's an adult, eating large rats and up to 2 lb rabbits. Living in a 5x2x2 melamine enclosure. He was a donation around 6 months ago so I don't know much of his previous history but he has a good appetite and no previous health concerns.