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rocks made from foam, epoxy and sand (lots of pics)


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Hey I thought Id share with you guys my diy fake rocks :D

In the past Iv always used real rocks, but they weigh a ton and to move the tank youve got to break down the whole thing, and for us renters its a real pain in the a..

For my new tank I wanted to create a land area and two water areas.

The usual glass divides look unnatural and making it out of real rock was out of the question. Fake rock all the way!

Im going to keep this brief..



foam in mould-


its two part closed cell foam used in boat building.

foam out of mould-


foam being carved-


foam carved- allcut.jpg

1st coat black sand from west coast and powdered soil, at a ratio of 8/2-


second coat of black sand and powdered clay, at a ratio of 2/8-


pic was taked before it was washed..

all done, I just did two coats and a touch up coat-


close up-


looks like stone to me :wink:

I had to paint epoxy around the waterline to stop it wicking up water-


450mm x 450mm x 450mm cube tank-


thanks hollywoods :D

before background-


after background-


'artists' impression of how it will look when done-


when finished the whole tank will weigh less than 30kg empty of water. FAR FAR less than it would if made from real rock.

If anyone wants to try their hand and make their own, Im happy to pass on advice from what I learnt along the way :wink:

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did you jusy use epoxy and sand and mix togeter or some thing else,cheers ant

nope I painted the epoxy on first(thin a coat as poss).

I mixed together very fine black sand and finely powered soil and clay(must be very dry) and sprinkled a thick layer over the wet epoxy.

wash, dry and repeat..

I found that black sand and silt comes out like river rock, and black sand and clay comes out like sandstone.

the most important thing is the sand and powdered soil/clay has got to be very fine, or it comes out looking like a blob of sand.

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Thats really good. Could you disolve out the foam with a solvent to remove the boyancy once the shell is hard?

not with the foam I used but i guess you could with polystrene.

If I was going to make hollow rocks Id buy some moulding latex and make a female mould from a real rock, then glass inside it, then fibreglass inside the mould. I would then coat the outside of it as I did the foam.

sounds hard I know, but thats what I would do...

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well done... :hail: any idea if fish would still lay on them or would the fakeness be detected??

I'd say they would. In the wild angelfish lay eggs on leaves, mine for example will hunt out anything long, fairly solid, and bright green, usually my filter hoses :x:x

Amazing work owen, thanks for sharing the process too!

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how u make the backround?

If you are interested in seeing a construction log of the whole build Iv posted it on a vivarium board - http://www.aquariacentral.com/forums/showthread.php?t=136377

oh and I have since come up with a way of making faux river stone out of hypertufer thats far less work and they sink too! but thats another story..

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