# Ways to make styro diy rocks sink without concrete?



## mia_ann (Dec 20, 2008)

Just curious. I haven't started them yet, but I was wondering about alternatives to concrete. I don't have a garage, so concrete will be difficult for me to do. Doing it outside is not an option at the moment, since I live in Wisconsin and it's FREEZING outside and everything is covered in snow lol


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## mia_ann (Dec 20, 2008)

I started them because I'm impatient :lol:

Here is the structure from 2 sides:



















Also, is there a fish safe paint I can use to paint this?


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## afoctober2 (Apr 7, 2007)

Don't know how this would work but possibly glueing some some gravel rocks using silicone or something.


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## mia_ann (Dec 20, 2008)

I was thinking of attatching two bigger tall, column shaped rocks to the bottom on each side to help weigh it down. I don't know, though, I'll have to try some sink tests to see how much weight I need


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## afoctober2 (Apr 7, 2007)

I'd like to see how it turns out I actually have similiar project at home but haven't covered it with anything.

I was thinking of using that hydraulic cement patch that says its waterproof.


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## mia_ann (Dec 20, 2008)

I can't wait until it's covered. I want to paint it instead of cover it with concrete. Any idea on a fish safe paint?


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## D-007 (Jan 3, 2008)

You could cover it with Drylok and then silicone it to the tank.


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## mia_ann (Dec 20, 2008)

D-007 said:


> You could cover it with Drylok and then silicone it to the tank.


One problem. There are water and fish in my tank already...

What exactly is Drylok? Is it something like cement?


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## D-007 (Jan 3, 2008)

Drylok is a latex masonry waterproofer. You can get it at most any hardware store (Lowes/Home Depot) and brush it on. Here is a link about it

Once it is dry you can put it in the tank.


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## mia_ann (Dec 20, 2008)

D-007 said:


> Drylok is a latex masonry waterproofer. You can get it at most any hardware store (Lowes/Home Depot) and brush it on. Here is a link about it
> 
> Once it is dry you can put it in the tank.


Thanks a lot! That sounds great. I do have more questions though.

Is it thick so you can make the surface appear irregular to give it a more realistic look, or should I make some bumps with my silicone before painting with drylock?

How expensive is it?

Is it heavy enough to weigh the structure down?

Do I have to worry about leeching?


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## D-007 (Jan 3, 2008)

Sorry ... my eyes glossed over the 'problem' part of your post.

I would try implementing some heavy rocks (real ones) into your DIY background at the base, then doing the Drylock and test it in the bathtub to see if it floats.


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## mia_ann (Dec 20, 2008)

Thats what I was thinking, some long, wide column shaped rocks, one on each side with flat bottoms and tops to weigh it down a bit.


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## D-007 (Jan 3, 2008)

Yes it is thick and I believe will give an irregular look.

Pricewise it is $22.95 per gallon.

No you don't have to worry about leaching once it has cured - that is the key part; let it cure for about a week with it being cold. Label will give good instructions/guidlines on this too.

Also, have a read of *this thread* as another alternative to concrete


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## mia_ann (Dec 20, 2008)

Thanks D, you have been most helpful :thumb: :dancing:


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## mia_ann (Dec 20, 2008)

That other product still requires a messy set of steps. I guess my main problem is I don't have anywhere to put concrete on, since I don't have a garage or basement and it's FREEZING outside.


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## gherlevi (Dec 16, 2004)

Don't underestimate how much styrofoam will float! Before you put a lot of time into decorative work, do a trial float of your project.

I know from experience, I spent days working on covering my false styrofoam rocks with cement, only to find out that they floated... severely!... and that silicone would have been the only option.

Fill your bathtub, try to sink a piece of styrofoam, and you'll get an idea of how much weight you need.


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## mia_ann (Dec 20, 2008)

Yeah, I was afraid of the gherlevi. I know it floats a lot. How much weight do you estimate I will need?


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## gherlevi (Dec 16, 2004)

> How much weight do you estimate I will need?


I can't really say, as the project I did was really "winging it."

I ran a post of the ongoing trials and tribulations:
http://www.cichlid-forum.com/phpBB/view ... highlight=

Don't quote me on this, but a really crude rule of thumb might be that anything more than 2/3 styofoam and 1/3 cement/concrete/rock will likely float. I learned that after trying to carve out the styrofoam from my rocks, and still finding that they floated!

Possible thing to investigate would be some other sort of inert material that you can use as the base or substrate. At the same time, you've already created what you want out of styrofoam, so see if other people have some ideas.

Good luck! Although nothing went as I planned, I had fun trying anyway...


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## a_c_arnold (Mar 7, 2008)

I've seen many post where people try to make bottom structures out of styrofoam. It's not a good idea and using silicon is about the only method to holding it down, outside of attaching it to some type of anchor. Styro is very difficult to keep down. If I need a structure for the bottom of my tank, I carve it out of the cement. You can also use regular stone in combination with cement to build a structure. Here's an example of a cement/rock structure that has been painted with drylok. I didn't have a garage either, it was made in the living room of my apartment.









Here's what it looks like in the tank


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## mia_ann (Dec 20, 2008)

Well, I'll see if maybe I can anchor it to some real rocks with silicone. A really big rock will probably hold it down :lol:

Or I'll just throw it away. The styro was really cheap, so it won't matter anyway


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## gmoses (Dec 4, 2008)

So i was all excited about making this as a nice cave for my tank. So I asked people for help...and they told me to use acetone to melt the styroroam...
Ok so i did that in parts all over and I added a 5lb rock siliconed to it...still it floated. the rock got it down a bit but not even fully submersible. So i went back and added holes and acetone every where and filled the holes with cement. Tested it and almost got it down...but still a few inches off the ground. I finally had to add another pound rock to it and now it sits comfortably at the bottom...
So good luck . 
Looking back i would use many thick layers of cement then poke some holes and use the acetone to shrink the styrofoam


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## Mcdaphnia (Dec 16, 2003)

If it comes to throwing it away, give or sell it to a reptile keeper.


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