Pacific Northwest Rock

[Reef_kid]

I have a cabin on hornby and visit there regularly the rock there is just a sandstone which is not a coral base (more of a sand base cement like rock)
hornby was formed by means of valcanic formation and may leech lot of chemicals into the water!! sandstone has a nice shapes though i would not say its porous! it is very heavy stuff. it will break down with wear of the water due to erosion.
you could try useing it as a base and putting liverock over it
i wouldnt better safe than sorry!

hope all gose well getting you tank up and going
try tufa rock you can get it relativly cheep!
cheers Dave