Turtles will pretty much bulldoze any plant that you put in there, so be prepared for that.
If you're using lighting with UV for your turtles, then you have a little more latitude with plants and aren't confined to just 'low light' ones.
I've had good luck with ferns: they hold up well in the limited light, enjoy the same humidity as the turtles and are not harmful if ingested. They are also surprisingly resilient and can bounce back well from tramplings if kept well watered.
Be aware that most potted plants are shipped from the growers with a generous supply of slow-release fertilizer granules in the soil which would be very harmful to you turtle if ingested: it's a good idea to shake ALL the soil off of the roots to get rid of the granules, and then put the plant into the substrate or new soil w/o any fertilizer.