REALLY, REALLY bad. Some say its wost than sand as it has a more rigid texture and could cut internally or cause impaction. I wouldn't worry just yet, as long as its eating it should be fine.
Thank you he is eating fine and I will not be switching. From reading think tile will be my choice. Now this may be a stupid question do leo's urinate and if using tile does it seep under the tiles?
No, geckos expel their nitrogenous waste in the form of a urate, which is the little white thing attached to the fecal pellet. Crushed walnut shells are a HORRIBLE idea! As mentioned, probably a worse idea than sand, if that is possible.
Geckos basically pass a poo that is feces and urine in one. It's not liquid like mammal urine, so no need to worry about it seeping under the tile. Occasionally mine will go right in the crack of the tile and some of it will break off and go in between, but I just make sure to lift the tiles and clean out from underneath them on a regular basis anyway.
very bad. I suggest going with tile also. I use tile in my gecko's viv and I love love love it! When they go potty I just wipe it up with a baby wipe and I am done. Much cleaner IMO.
I used to have wallnut shells sometime last year and I had no impaction problems. I switched only because it seemed messy. Then again, Im sure there are people who have problems. I think its just chance. Same thing with sand. I've heard people that have and have not had impaction with it. Some leos take to it, others don't. Whatever you're comfortable with.