using concrete to build a reef..?

[RUCoralGuy]

So I'm designing a new display tank, its a 200gal display in the main lobby of my building. I want to build a natural looking reef structure without having to buy hundreds and hundreds of pounds of coral base rock. Any suggestions? A friend mentioned using concrete and molding it how i want around a plastic frame. He also said how someone told him once that they used macaroni mixed in with the concrete to allow it to become porous. Basically i want to build a structure large enough to cover most of the 3 sides of the tank.

 

[Anonymous]

Aragcrete and other similar aragonite-based concrete is what you are looking for. Do a search and you will find tons of article here and elsewhere on the net.

 

[Tole]

http://www.garf.org/

Has lots of info on making concrete live rock substitute.

Unless you use some kind of light weight filler the rocks will weigh a ton. I would not recommend any filler that will decompose. Dead or decomposing matter is bad for the water in the tank.
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You must take the time to cure the concrete in water before putting them in the tank. Curing will leach the alkaloids out of the concrete. Uncured they will crash the PH of the water and release other nasty chemicals.

 

[chris&barb]

spray foam insulation, the stuff that come in a can for filling cracks around windows.a day or 2 of cure time and it wont leach anthing.you can smear it around the way you want, its light,you can poke holes in it.

 

[Anonymous]

If anyone use foam, you need to make sure there are skeleton for support. Most application is onto a panel, but the original poster want a structural application.

 

[RUCoralGuy]

Thanks guys!
What I plan to do is mix up some aragocrete and pour it onto some eggcrate that i've measured for the walls, let it set, and then build stuctures and whatnot onto my new rock wall. Do you think this is a good idea?
most things i've read about aragocrete say curing time is 6-8 weeks, then i read somewhere else that it can be cured in a few days in water with a lot of water changes and water flow.... which do i believe?

 

[Anonymous]

You have to cure it until the ph in the curing water is stable at or around the ph that you want in the tank, then re-cure it in salt water because the chemistry is different between salt water and the arragrocrete. Minimum 6 weeks is what I would recommend for that big a casting. Then 2 weeks in salt water. You are probably still not going to be ready then.... IMHO This is why arragocrete is not as big a boom as garf would like.

 

[Len]

Hi Tole,
:welcome: