Lava rock?

[mbjrc]

Hi, I am going to build a cave from pvc and rocks siliconed to the sides to hide it, basically building a hill. I was wondering if lava rock pieces would be ok to use. If not what rock would you recommend. I will also have plants planted on this hill.

Thanks

 

[Jacko]

Lava Rock should work, but from what I have seen and heard, it can be hard to silicone to things because of the dustiness. It might be easier for you to just put the pvc tube in then pile the rock around it since Lava Rock tends to lock together really well. At least in my experience it does.