To be on the safe side, define the size of a flea!
If the bug is no bigger than this ° it could possibly be a mite. However, snake mites tend to be dark brown/black or reddish. If it was bigger than this ° it is not a snake mite. Beige is not a color I've ever seen used when referring to snake mites.
If you want to be on the safe side and see if there could be mites, replace your substrate with paper towels. If mites are present, you will know very soon.
If I was in your place though, I wouldn't be changing anything unless I suspected snake mites or saw evidence of another type of bug infesting the tank.
Keeper of 5 snakes, leopard geckos, 1 green iguana, 20+ tarantulas, 2 dogs & a bunch of rats!