So here's an interesting problem. Turtles are supposed to need these special lights that give them certain nutrients or good rays or whatever. They're called "basking lights" because the turtles climb up out of the water onto their rocks and bask in the warm light.
Except that Howard (who, by the way, is now about the size of a half-dollar) never comes out of the water, and if I were to put a few inches of mud in the bottom of his tank, I'm sure he'd be even happier. I still leave the light on, but I'm starting to think that's not such a good idea.
As anyone who has had tropical fish knows, keeping the lights on encourages algae to grow on the rocks and glass, though not on the fish. But when the critter in the tank is kind of like a rock, well, there's a reason they refer to old snappers as "mossbacks."
So when I clean Howard's tank once a week, I take out the rocks, scrub them and cover them in boiling water in hopes it will discourage the microbes. While this happens, Howard is in a shallow bowl. You have to understand, Howard does not like being handled and I have no particular urge to make him uncomfortable, so I take him out of the tank and put him in the bowl with some water, and then put him back as soon as his little habitat is ready for him.
Only I do pick him up long enough to gently scrub his back with a soft toothbrush and try to take off the algae. If you look at this picture, you'll see a few bits of algae remaining, along with a lot of kind of fuzzy stuff which is the result of him growing ... he sloughs off bits of shell-skin on a fairly constant level.
What you'll also notice is a lot of green on his head. I don't think there's anything I can do about this, because even if his head would stand up to being scrubbed with a toothbrush, I'm sure his little turtle psyche would not recover from the insult to his dignity.
Since I will probably have to use the basking light to keep his water relatively warm through the winter when the rest of the house is somewhat cool, and he will definitely not be crawling out onto the rocks where he might actually dry off from time to time, it's entirely possible that, by spring, Howard will have a nice shock of bright green hair.