Any way to potty train a Russian?

[Shaggy99]

I have a male Russian living in a 16 square foot enclosure. Every single day he takes a dump on his basking spot, which is a big rock that doubles as a roof for his cave. The only way to clean off this rock is to take it outside and hose it off, which becomes a problem when the hose freezes in the cold winter weather. Is there any way to get him to go to the bathroom somewhere else?

 

[ZEROPILOT]

It seems like he already chose his spot.
Pretty much, they just poop when and where they feel like pooping.
Mine poop a lot in their water pools.
Yep.
The same place they all come to drink.