# DIY Fake Rocks



## Slimo (Nov 1, 2010)

I did a lot of fake rockwork in my past "carreer" using polymer clay, polyurethan, epoxy. But the best looking rocks, i find, are always made with concrete. 
Here's a few test run I have been working on. They are all flat based, but once I do the real thing in for the aquarium, I use an iron frame an build the rocks higher. Takes about 6 - 8 weeks to cure an then they are PH neutral.


----------



## Fish_Man (Apr 9, 2010)

Pretty awesome!


----------



## ameekplec. (May 1, 2008)

Looks great! hehe, the brown ones look like big animal poos.

Are you concerned about the iron frames rusting out in the tank? Why not another material like carbon fiber?


----------



## Dabigmandan (Nov 13, 2010)

I actually made a bunch of these a while back. I didnt use any frames though... all I did was use less water in my rock mixture which allowed the mixture to be dry enough to build taller rocks. It did make them a bit more brittle though.


----------



## Slimo (Nov 1, 2010)

ameekplec. said:


> Looks great! hehe, the brown ones look like big animal poos.
> 
> Are you concerned about the iron frames rusting out in the tank? Why not another material like carbon fiber?


LOL, I guess they do! but the final product looks like eroded tropical laterite river banks, very natural looking.

No I'm not concerned about Iron in the tank. most of the wires will be covered by the concrete and a bit of rusting iron is not a concern in a freshwater tank. 
I tried it many many times. in fact if you add EDTA, this bonded iron in the water becomes available for plants to use.


----------



## JAM (Dec 14, 2010)

*What did you use to color them?*

Can you teach us how you did it. Where did you buy the materials? What kind?


----------



## Slimo (Nov 1, 2010)

*Instructions*



JAM said:


> Can you teach us how you did it. Where did you buy the materials? What kind?


The mix is very easy, forming the rocks is where the "magic" is...

Basically you need to use Portland cement as a base and mix it with other materials and/or pigment to get texture you want. But always use about 1 part volume Portland cement for 2 to 3 part of the other materials.

You can use:

-Sands or gravel of different colors
-Perlite or vermiculite
-Dry red clay
-Peat moss (give a real natural look)
-coco fiber
-red oxide pigment or any other natural non toxic pigment. Careful some pigments are safe in fresh water, but not in saltwater.

You need to mix this with the right amount of water: until its moist and workable but not wet. add water a little bit at the time.

Once you mix is ready, wearing glove form the basic rocks and start sculpting using knives or a trowel, anything you can find. You can use stuff like sponges to texture the rock.

Let it harden a little (1 hour) and do some finishing work.

Once air cured (2 days), you need to cure the rock in water that you change every day for 6 weeks at witch point they will be PH neutral.

for bigger rock-work use steel mesh reinforcement (in fresh water only and no galvanized).

The best thing is to practice before on a few test rocks like i did before you undergo a big project. This also allows you to find the mix that will work for you.

That's pretty much it....


----------



## gucci17 (Oct 11, 2007)

They look really nice. How heavy can they get? I was thinking it would look amazing if you could build a similar style to the aquaterra backgrounds and even have overhanging rocks using your iron framing and steel mesh.


----------



## JAM (Dec 14, 2010)

Thank you! Salamat! Shokran. 

Very informative! I might do that this summer.


----------



## 50seven (Feb 14, 2010)

Cool! Never thought of doing this for a freshwater tank...

Your rocks look pretty real too. Great way to make your aquascape just the way you want it.

Though I also agree that some of them do kinda look like turds, LOL

I agree, this method would not be appropriate for saltwater, as the metal would surely rust, and the rocks for saltwater LR needs to be made porous in some way. Search for my thread on DIY live rock for that.


Sent from my HTC Magic using Tapatalk


----------



## Slimo (Nov 1, 2010)

gucci17 said:


> They look really nice. How heavy can they get? I was thinking it would look amazing if you could build a similar style to the aquaterra backgrounds and even have overhanging rocks using your iron framing and steel mesh.


the cement one weigh about as much as real rocks. But you can make them lighter by making them hollow or build they over Styrofoam. if its to do a background:

just lay the aquarium on its back, 
cut a sheet of steel mesh on inch shorter of the aquarium back.
lay your rock mix and sculpt it while the tank is on its back.
Make sure the concrete has a good base on the aquarium bottom and you should be fine. You can also put a piece of .5 inch Styrofoam in the botom of the tank before you build the rock work. this way the weight will be distributed. But it not event necessary because the cement mix will lay flat on the bottom and the weight will be very well distributed. In fact you could fill the entire tank with concrete and it would hold up, because of the perfect weight distribution.

What breaks a tank is when you have lots of weigh on a single spot: like a big rock that has a pointy edge and you happen to place the edge on the tank bottom...i speak from experience!!


----------

