SAFE materials for saltwater.

[kittyhazelton]

I got this idea to make a really interesting rockwork structure for my FO saltwater tank. And I'm wondering what kinds of materials are safe for this kind of thing.
Foam? (Styrofoam and/or the squishy kind)
Fiberglass and resin?
Paints? What kind are fish safe?
Concrete/cement?
Names of brands, ingredients, specific types of things are preferred.
I am going for a lightweight design that will stay sunken once it's done. so nothing too buoyant.
Heres a quiky drawup of what I'm thinkin....

 

[muckieman]

i shure cement will work guik dry cemet or the kind you use ti pach up a pond. why not life rock......

 

[Nic]

carib sea aragonite sand and type 3 portland cement do a search its arround on this site but google is better thats how people make there own live rock

 

[muckieman]

oh ok...cool

 

[kittyhazelton]

i shure cement will work guik dry cemet or the kind you use ti pach up a pond. why not life rock......

Live rock is freaking heavy. I want it to be easily dissasembleable, and to have the amount of liverock I would need to build that kind of structure would equal incredibly expensive. Around here liverock is anywhere between $10 and $20lb. My tank is a 110gallon, and it's older so I'm also worried about having that much wieght consentrated on only a small area of the bottom of the glass.

 

[Rivermud]

a website to check out would be http://garf.org They have DIY instructions for making live rock out of Aragonite and Cement