I recently got a 7ish-year old ball python, who came with a 10 gallon tank. I'm looking to rehome him in something larger, so I got a 15 gallon tank on OfferUp. I was washing it out today in preparation for moving him in, and I noticed that there's some blue staining/buildup on the inside of the tank around where a water line would be (guy I bought it from said it was used as a fish tank, but he didn't specify what kind of fish). I'm thinking it was a water dye of some sort or something left over from its fish days, but does anyone know if it's okay for snakes to be around? Some antibacterial dish soap and elbow grease got it off of the glass walls, but it's still staining the glue joints.
Thanks!