Clean water... Moss barrier?

[Amber October]

So, I'm getting ready to redesign an enclosure for Torrence. I'm trying to figure out how to keep his water clean. The moment I set it down I accidentally knock dirt (coconut substrate) in it. I saw pictures on here of someone else's enclosure and they had moss surrounding the dish. I really like that water bowl set up and thought it might help me.
I'm wondering if it's safe for a Russian Tortoise. The thing is he does try to eat anything green, which is why I have to keep an eye on him when I let him wander around the house. I'm planning on adding plants as well, so maybe the edibles will distract him?
If you think it will help, what type of moss? Thank you.

 

[wellington]

Some will line the outside of the dish with flat rock. It helps to get the substrate off before they enter the water dish.

 

[Amber October]

Some will line the outside of the dish with flat rock. It helps to get the substrate off before they enter the water dish.

Thank you.

 

[turdle yerdle]

You can also put slate underneath

 

[Amber October]

You can also put slate underneath

Thank you.