I've read on here that sometimes this causes a problem with toxins
I have a exo-terra cave made for reptiles that my ryan loves
you can order from here for example or try and find one cheaper nearer you.
Here's Ryan guarding his cave
EDIT mine is the medium size, but there are small medium large and extra large available.
I *really* like that cave.
I've seen that pic of ryan before and admired his cave but didn't know where to get one like it. I bought a cave (not as nice!) at my lfs but when I got it home I found that it was broken so I took it back. Unfortunately they didn't have any others so I was out of luck. (btw, I was just in there today... and saw the broken one was back on the shelf! )
i have had coconut caves in my tank for 4 weeks now and a friend of mine has used them for yrs on end with no porblem at all just prepare them right once your dont cutting them , boil them for 10 min then rinse off change the water repeat 3-4 times to get the tannis out all will be fine