Polystyrene! HELP!

[purpleturtle89]

ive been watching a lot of videos and want to attempt at making a waterfall/ stream but i dont know what to coat it mortar concrete etc (although them 2 could be the same thing for all i know) anything i shouldnt buy watch out for and how to seal it? thanks

[Heatheranne]

Non-sanded grout. Heres a good web site that shows you the steps.

http://www.lizard-landscapes.com/how...waterfall.html

[purpleturtle89]

seen a few of his videos, just cant find any sealer or not sure what im looking for :/