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I just read that if you're setting up a tank that will include both a sand substrate and rocks, you should put the rocks on slices of styrofoam.

Supposedly this is to prevent the entire weight of the rock from being concentrated on a single grain of sand and cracking the bottom.

This is the first I'd heard about this, and I'm wondering whether I should re-vamp my 20-gallon long, which has rocks -- the largest of which is about the size of a baseball -- sitting directly on sand.

Opinions?

I've never heard of doing that. I've had some pretty large rocks in my tanks and have never had a problem. I doubt that you will either. I sure wouldn't be tearing down an established tank to do something like that.

Jim

---

Water, taken in moderation, cannot hurt anybody. -- Mark Twain

Why not just lay the rock on a thick layer of sand, thereby balancing out the weight even moreso than with the styrofoam? Or, one could place the rock in first, THEN add the sand.

Last edited by Cup_of_Lifenoodles at 22-Apr-2005 22:26

Never heard of styro being used inside a tank without being coated prior to use. Stryo does tend to fall apart easily after all .
I have heard of egg crate being used....that's the grate type thing that goes over (or rather under) floro lights in buildings...you can find it in most home improvement stores in their lighting section.

^_^


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And join me for a swim tonight"

I've heard of egg crate being used but only with really big or lots of rocks in big tanks. Such as cichlid tanks or saltwater. My 55g has a 12" long geode sitting on a thin layer of eco complete. As well as a large cave directly on the glass.

LMuha

Styrofoam would be one of the last things I would put in a tank as it breaks down and it will (unless properly prepared.) Not only will it break down if and when a fish swollows a piece it will swell up in its stomach and adventually kill the fish.

In all my 35+ years I have never heard of such a thing.

Keith

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Styro won't swell...it's already expanded.
If a fish were to eat it I'm sure it'd simply pass thru, however I still dont reccomend using it untreated. The small pieces will float...right where fish are used to looking for food increasing the risk of them eating it.
From experience I can say that my fish seem to spit out any pieces that got into the tank...not that I intentionally drop styro pellets in the tank .

^_^

[hr width='40%']"Put your soul in the water,
And join me for a swim tonight"

Just put the rocks on a bare bottom tank & then add the sand.


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small rock towers are ok with just sand. the problem isnt the weight on a single grain of sand the problem is them either falling over or fish digging under them and causing a preasure point. preasure points are only a worry with some serious weight and severly uneven rock like live rock in salt tanks.

tank bottoms are usually temperd and are built to withstand serious weight from both water and liverock. if your just doing a few simple rock formations i wouldnt worry at all. only when you get into serious weight does it start to be a concern.

need something to compare it to....think of a large saltwater tank. local fish shop or a picture on the web. all that live rock might be on eggcrate but doubt it. the biggest concern is falling rocks. if its stable then it should be safe. have fun

Yeah, that's what I did when I set up the tank -- rocks first, then sand. But I was just reading one of Ad Konings' books on Tanganyika cichlids, and here's what he says:

"Large rocks are best placed on a thin sheet of styrofoam to protect the bottom glass (if there are no filter plates). It is not the actual weight of the rock, but the possible concentration of it on a few sand grains, that may crack the glass."

I don't think the rocks in my tank are big enough to worry about, and even if they were, I'd have the same concerns about putting styrofoam in the tank as everyone else. But Konings is certainly a reputable source, so I thought I'd pass it on.