I nearly always have plants in my turtle tank - the way I see it they'd have plants in the wild so it can't be a bad thing to include them in my set up!
Sooner or later they do eat them but this only forms part of their natural diet anyway, although it does make the tank a little more messy than you might usually expect and clogs the filter up a little quicker than normal.
On a big plus side it improves the water quality, supplements the diet and gives the turtles something to play with (if you have fish in your set up it also gives them somewhere to hide - until/unless they become dinner :twisted: Plants also make the tank look more attractive too - although I don't think the turtles'll care too much about that! lol!
I've used water lettuce (I've found these last slightly longer than the others) elodea densa and amazon swords. They all got eaten eventually but sure looked pretty while they last!!
Hope that helps - let us know how you go.
I keep plants in my current (Vision 180) setup and they seem to munch on some and leave others alone. The Vision 180 was my first fish tank and it was originally setup as a freshwater fish + plantation tank (with soil, C02, etc) and worked a treat.
The idea I was contemplating was to set the tank up (with a sump) and let it mature for a good few weeks so that the plants will start to grow. This way, if they are nibbled, they will stand a chance at repairing themselves because they are established. :?
Hmmmm :? This isn't absolutely cert info but from what I've managed to find out turtles are better off without substrate (whether it be soil or gravel) largely cos of cleanliness issues (I'm guessing the mess that accumulates in the tank depends on whether your a 'separate bowl feeder') and the minor risk of ingesting the substrate but also due to the nitrate pockets that can form within the substrate that the turtle will disturb when getting upto their usual impish behaviour and sticking there snout in everything they can! These nitrates can be quite bad for the turtles due to the amount of nitrate within the limited space a tank provides. In a huge set up (e.g. indoor pond) where it is slightly easier to simulate the natural experience it may be possible but I'm not sure I'd attempt it in a tank.
As I say this info isn't carved in stone or anything - just bit's I've gleaned from my own research along the way to turtle happiness!
The turtles I have at the moment are still very young, so I'd imagine the destruction capacity would grow with their size. Eering on the side of caution along with your valid points, I'm re-thinking it all through. :lol: