Mike @ Waggy told me that they do ok, however you CAN'T keep moving them around, and they move on their own to wherever they go. So, you'd put it in the tank, and it moves to the back, or wherever it wants to go, and you can't move it after that point. For what it's worth
I've always heard they'll just go to the back of your tank and you'll never see them anyways. Plus they only live about 6 months in a tank. But then again i'm a newbie so don't take my word on it !!