I've always let all my water turtles throughout the years have access to elodea (aka Anacharis). Right now I only have a juvenile stinkpot but he likes to nip at it every now and then. RES have more omnivorous diets then musk turtles, so yeah go for it. I also found that RES really like to eat water lettuce so if your LPS has any, plop a few in your turtle’s tank.