What size tank does an adult Mississippi mud turtle need?
You’re not the same guy that was going to buy the “Mississippi mud turtle” that turned out to be a stunted snapping turtle, are you? If it is in fact a Mud turtle, a 20L is large enough to house it as an adult, but as with all animals, the more space you can provide for it, the better. Yor set-up sounds good, you shouldn’t have any trouble with the little guy. Mud and musk turtles have big personalities. They’re always active, poking around their tanks looking for things to eat. There’s nothing cuter than a musk turtle with it’s neck fully extended, picking shed skin from between it’s hind toes!