When I suggested a bog turtle as a pet, I was confusing common names. The turtle I'm thinking of is commonly known as the musk/stinkpot turtle. The are semi-aquatic turtles, meaning they only need a small puddle of water to soak in but not swim in. They'd need half the tank to be dry land. They do only get about 3-4 inches in size, whereas most commonly kept fully aquatic turtles typically grow closer to a 1' in size. I do believe musk turtles are capable of releasing unpleasant smells from their glands, so maybe it isn't a turtle to have as a pet. My advice is to stay away from all turtles unless you think you will have the dedication to care for one throughout the decades.
Sorry, but ALL musk turtle species need plenty of water for swimming. And actually they rarely leave the water to bask. Captive Stinkpots rarely release musk and the same goes for the wild ones. I've caught dozens of stinkpots over the years and I've never been musked. Not to mention I own a breeding pair, see below.
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Now Mud Turtles will sometimes use extra lands space you provide but they to are primarily aquatic turtles. I have a Red Cheek Mud Turtle that rarely ever leaves the water to bask or explore on land.
But you are correct, most species stay quite small.
