So I put the cuttlebone in the tank but it just floated around and the turtles couldn't get ahold of it. I kept thinking I needed to anchor it somehow and then I got it.
Went to Walmart and got a $1 small dog chain. Cut 2 holes in the cuttlebone and used zip ties to hold the cuttlebone to the dog chain on both ends (dog chain for weight to keep it on the bottom).
Just an idea.