Algae grows on turtles’ shells naturally. However, it can hide infections or injuries, and excessive buildup can get in the way of the turtle’s ability to absorb UVB and heat while basking. In rare cases, algae will start to grow under partially shed scutes (shell scales), and shell rot may develop as a result.
Dark green algae that grows in carpets or patches is fine. However, if you notice a long, stringy, slimy type of algae growing on your turtle’s shell, that is cause for more concern.
If your turtle’s shell feels slimy or slippery, but you can’t see any algae, it’s most likely bacteria — and as you can imagine, that’s not a good thing. Fortunately, the treatment for bacterial film is similar to the treatment for algae.
Treatment
Make a routine of regularly scrubbing your turtle’s shell with a soft toothbrush and room-temperature water in a separate container from the turtle’s tank or pond. Depending on how much algae has built up on your turtle’s shell, this can take some time. However, be patient and GENTLE — remember, turtles can feel their shells just as well as you can feel the top of your head.
After you are done with your turtle’s regular shell-brushing, disinfect the container with F10SC, chlorhexidine, or bleach solution.
Prevention
There’s no way to truly prevent algae buildup in your turtle’s tank. However, there are some things you can do that will help (note that most of these things are congruent with good red eared slider husbandry):
- Keep the tank clean
- Scrape algae off the walls and décor regularly
- Keep the water moving with a filter and/or aerator
- Do not place the tank near a window
- Perform regular water changes
- Don’t leave excess food in the tank
- Use live plants
- Add algae-eating fish (might get eaten by turtle)
Do not add algae-prevention chemicals to the water, as these may be able to harm your turtle!
In fact, some algae in a turtle tank can be a good thing. While it does look a bit messy, it can help clean the water and make a healthier living environment for your turtle.
References
How to Easily Clean a Red Eared Slider’s Turtle Shell. (2019, February 12). TurtleHolic. https://www.turtleholic.com/clean-sliders-shell
Yates, B. (2019, July 17). Turtle First Aid – Turtles and Algae. All Turtles. https://www.allturtles.com/turtles-and-algae