Leonidas isn't soaking in his water bowl but just today, I've picked him up and found 4 black dots on my hand. I then squished them between my desk and my nail and they popped, so that made me thing those were mites. Since he's not soaking in his water yet, does that mean I caught it early on?

I plan on changing his substrate and cleaning his whole tank tomorrow once I buy the supplies. Any other tips on how to take care of this problem?

Thanks in advance!!