# Making my own rocks.



## ilikebeer1985 (Dec 21, 2007)

So, you know how everyone is making there own rock background with styrofoam. i was thinking, can i cut out rock shapes and drill nice holes and cover them with cement, they would sink right?
that way i could pile em up, and match a diy background i want to make?
has anyone done this?


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## a_c_arnold (Mar 7, 2008)

Dude, just make the whole thing out of concrete. Concrete is cheap and you have to cure it any way. If you want to cut down on the use of concrete, just get a field stone and concrete over top of that to get the size and shape that you want. Here's a structure that I made with a combination of fieldstones and concrete.










Here's a pick of the structure in the tank


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## Mcdaphnia (Dec 16, 2003)

There is a huge thread by InsaneReefer on doing exactly this plus many variations on Reef Central. One of the variations is instead of styrofoam, they mix rock salt or water softener pellets with the concrete, as much as 50%. When you soak the hardened rock in water before putting it into a tank, the salt dissolves, leaving many holes.


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## Hoosier Tank (May 8, 2007)

You can also do an internet search for "Aragocrete". Its a mixture of Carib-sea aragonite and cement. You make a sand box mold and you can have rocks and caves as big or any shape you want. That way you don't have to guess on how much styrofoam to remove to make it sink.


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## Dewdrop (Nov 20, 2007)

Love that background a_c_arnold! I like the idea and the looks of those type backgrounds but don't like the space you loose because of them. With deep caves like that built in, you would be getting some space back. I like it! Probably makes the fish harder to catch but I'm not afraid to get my hands in there to corral em :lol: . When I get my bigger tank, I just might have to try making one of those backgrounds.

Making a note of Hoosiers project in my fish notebook too :wink: .


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## ilikebeer1985 (Dec 21, 2007)

cool, i had in mind, shaping a piece of styrofoam into a rock. Putting 2 holes sp fish can swim through them. then covering it all with cement.
Will this float? or sink?


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## Mcdaphnia (Dec 16, 2003)

ilikebeer1985 said:


> cool, i had in mind, shaping a piece of styrofoam into a rock. Putting 2 holes sp fish can swim through them. then covering it all with cement.
> Will this float? or sink?


 Probably both. The cement will chip off and sink. and the foam will float. The best way to keep the cement from chipping off is to first tie synthetic yarn all over the foam before cementing it. You can drill holes through the foam so you can thread the yarn through where needed to lie flat against the foam. The same yarn is used to make spawning mops for killifish and rainbows, so it is safe in the aquarium. Also make the cement thicker on the bottom to avoid the cave wanting to flip over.


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## exasperatus2002 (Jul 5, 2003)

What about painting a waterballoon with cement to get rock shapes and then when dry, pop the balloon and pull it out. That would help cut on weight, and give you different rock shapes. To keep the balloon from shattering when popping, put a piece of tape on the balloon & then pierce the balloon where the tape is. Then you can control the water coming out and you dont have to fight to get little bits of balloon out.[/list]


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## Mcdaphnia (Dec 16, 2003)

I've never heard of using water balloons, but using the tube-like birthday party balloons for twisting into animal and flower shapes is an old aragocrete standard. So is inflating a plastic glove so you end up with a central cave with five or six entrances (six if you leave the knot at the wrist uncemented which is a good idea.) Whether it's a balloon or a glove, all the pieces of plastic loosen, unless you cemented in a knot. Always leave the knots sticking out if you can.

I can only see disadvantages to using water balloons. The pinhole would probably get me in the face, or shoot across the fish room and short out whatever piece of electrical equipment would cost the most to replace. :lol:


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## gherlevi (Dec 16, 2004)

I made my own rocks out of cement and styrofoam, and I didn't want to take up too much space in the tank with a full DIY background either. I hope this link works:

http://www.cichlid-forum.com/phpBB/view ... highlight=

First time I made them, the rocks floated... even after a 2nd coating of cement and hollowing out the styrofoam!! The final result was made almost entirely from cement.


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## gmoses (Dec 4, 2008)

i didnt initially think about the whole floating thing...so now i decided i was going to silicone this to a rock... any thoughts


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