Ok thanks Yvonne!!You can lightly scrub him with a brush, but the white won't come off until he sheds.
You could perhaps put a few Chinese Algae Eaters or Siamese Algae Eaters in the tank. I have a group of them and have yet to see any algae on my turtle. The encounters they have with him are brief but they seem to take care of it.
I think eventually they will serve as fish steak for your turtle. Another thing, chinese algae eater not really good for algae control, especially when they grow up. Siamese is okay.Oh, I like that Idea. Ok, thank's Randi.
They are fast swimmers so I find them being snacked on unlikely. If you provide driftwood or rocks that have places to hide, your turtle won't even see them. And if it does, the chances of the turtle getting to it are slim to none.
I don't believe that ammonia is the cause of algae. Ammonia is present when there is a lack of good bacteria and you generally do not see algae in a tank that is not established or cycled. I believe that poor water conditions (caused by over feeding, poor filtration, not enough water changes, a tank that isn't large enough to sustain), high nitrates and phosphates, as well as lighting (light on for long periods of time, new uvb bulbs or expiring bulbs where the wavelength has changed, sunlight from windows), will contribute to algae.
I would like a better picture of the original posters tank because I have a feeling it may not just be algae and perhaps may have some cyano bacteria in the tank.