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Got a question for everyone. Every once in a while I'll notice some algae builds up on one of my RESs shell. Typically I clean it just as quickly as I notice it but is this harmful and what am I doing to cause such a thing?

Is your tank near a window? This may cause excessive algae growth. Algae on your turtle's shell isn't harmul, as long as it's somewhat under control. Try scrubbing it with a soft tooth brush, don't be to physical.

Make sure your turtle is getting enough calcium in his water to keep his shell hard. If you need to, add a calcium block to his water periodically. In my past experience, I noticed that turtles with harder shells are less likely to get algae growth. Turtles that are in rapid states of growth (less than 4 inches in length) are more susceptible to algae growth & soft shell than the adult turts & will need more calcium.

Also, as RESowner mentioned) using an old worn-out (soft) toothbrush on his shell every few days (brush lightly) will help prevent algae build up too.