Styrofoam can be used to make aquarium features, but it is usually covered with food grade concrete related materials. Look into products with the name Sika.I am interested in creating a cliff wall as well, but not sure how to foam to make it look natural..
I didnt want to create my own rocks and stuff. I was going to look for lava rock (so far no luck in socal-oc area, only place i found so far is $2/lb which is a bit pricey for my budget) and then foam it in to make the high cliffs I want and caves I want. I just wasn't sure what they use to blend the rocks and foam together.. It looks like they just poor sand on top, but it looks so natural that I'm not sure how the foam and lava rocks will turn out.. I am still on the hunt for any other type of rocks i can use but this is my first time actually making a scape so I am a bit loss.. tanks been sitting for 2 months.Styrofoam can be used to make aquarium features, but it is usually covered with food grade concrete related materials. Look into products with the name Sika.
The concrete can be colored (concrete, masonry, rock, some landscape stores carry coloring for concrete).
The basic idea is that you carve the shape you want into the Styro, making the gouges or caves larger because when you add a layer of concrete they will get smaller. Carve it to look like natural rock with splits, grooves, or whatever.
You can also use expanding foam filler to help out. It can really make root-like shapes very well. There is a black pond material, and the yellow construction grade product is also fish-safe.