# Adding Rocks to Glass Bottom Tank



## Nyboy (Mar 4, 2017)

I would like to add some rocks to my tank. The bottom of my tank is glass, I am worried about weight cracking glass. How much weight can I safely add to 50 gallon tank? When I was a kid tanks had slate bottoms, wish mine now did.


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## Deeda (Oct 12, 2012)

You can add as much rock as the tank will hold, just be sure the rocks sit on the glass and not the substrate and you don't drop any rocks when you are placing them in the tank.


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## nodima (Oct 3, 2002)

snorkel3 said:


> You can add as much rock as the tank will hold, just be sure the rocks sit on the glass and not the substrate and you don't drop any rocks when you are placing them in the tank.


+1


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## Coachfraley (Mar 19, 2017)

I always put a layer of eggcrate (plastic light defuser) on the bottom. I make sure the rocks are up against the plastic. This spreads the load of the rocks out over the whole bottom, preventing pressure points that would cause cracking.


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## Nyboy (Mar 4, 2017)

Thank you


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## DJRansome (Oct 29, 2005)

The egg crate won't hurt (except possibly appearance) but the engineers have convinced me that it really does not serve a purpose.


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## farmhand (Dec 7, 2015)

snorkel3 said:


> You can add as much rock as the tank will hold, just be sure the rocks sit on the glass and not the substrate and you don't drop any rocks when you are placing them in the tank.


What about granite that sits on the bottom at small points?



DJRansome said:


> The egg crate won't hurt (except possibly appearance) but the engineers have convinced me that it really does not serve a purpose.


Is there a link that shows what the engineers have come up with? I just bought some egg crate but would rather not use it.


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## DJRansome (Oct 29, 2005)

No you just have to search topics. May not be easy...sorry...just something that has stuck in my mind. If the bottom of the rock concerns you...knock off the points a little to make it flatter.

I have tanks both ways. None of my rocks are flat on the bottom...but none of them are diamond hard and pointed either. FWIW.

For the purpose of gaining height (not to avoid glass breakage) I often stack my rocks on man made items. Blue stone pavers. Terra cotta saucers covered with slate tile (the catfish love the covered saucers). Things like that.


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## Aaron S (Apr 4, 2015)

I wish you had mentioned the saucers when I was making my tank! I put some egg crate only under my large rocks (cut it down to size of the bottom of the rock) so that it wouldn't look bad if they dug around the tank, but I would have preferred something like a saucer as it would be easier.


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## dorsal73 (Aug 30, 2016)

I was a bit concerned about large rocks(40lbs+) sitting direct on the glass of my 75g, I ended up using some Dap aquarium sealant and glued some non-toxic styrofoam to the bottom of the three largest. I got a little bit more height for the larger stones and put smaller rocks at the base so no styrofoam is seen. Fish do not seem to bother or chew on it. I did have some "floaties" when setting the tank up, but I got them all removed before adding fish.


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## Iggy Newcastle (May 15, 2012)

I have some boulders in tanks that easily weigh over 50 lbs. Right on the glass. The glass and silicone takes the weight. Just be careful lowering and setting up.


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## JRW81 (Mar 14, 2017)

I read somewhere that for bigger rocks you could cut a piece of pvc pipe thin enough that your sand covers it and drill holes in it. Place that on the bottom and put the rock on it to spread out the pressure and then put sand around it .


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## Iggy Newcastle (May 15, 2012)

Cut lateral?


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## DJRansome (Oct 29, 2005)

The question is why.


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## JRW81 (Mar 14, 2017)

Cut it across. Cut off like an inch or so from the pipe so it would be a circle. I just like it better than having the rock directly on the glass. Have heard a lot of stories about tank bottoms cracking from rocks.


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## Iggy Newcastle (May 15, 2012)

Those stories must be impact related. Like a tower of rock tumbled in the tank. Or a poor reseal job.

This is a video showing a 10 gallon tank being filled with rocks-


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## JRW81 (Mar 14, 2017)

Yeah I agree most are probably impact related. I guess I would just rather be safe than have a problem that I could have easily prevented. I tried to find something about using the pvc pipe because that would explain it better than I can. Apparently it's used more in reef tanks but I like doing it that way and just figured someone else might like that option also


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## DJRansome (Oct 29, 2005)

But a base is not going to help you unless it falls on it's bottom...does not really solve an impact problem.

And what the engineers are saying is that "spreading the weight" is not necessary.

So I'm trying to understand what problem it solves? And why doesn't the substrate/water trapped inside the PVC, in spite of the circulation holes, become a nitrate trap?


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## nodima (Oct 3, 2002)

JRW81 said:


> Cut it across. Cut off like an inch or so from the pipe so it would be a circle. I just like it better than having the rock directly on the glass. Have heard a lot of stories about tank bottoms cracking from rocks.


Not trying to be a pain or worse, but I'd love to read or otherwise hear about a first hand account of such an incident. Seems like it is always the vague post like this one, or the "a friend of a friend told me..." I've been in the hobby for 30+ plus years, and have not heard a reliable source of such a mishap. I've experienced trim breaking, seals letting go, and other issues and have stacked my tanks full or rocks for most of that time, including through an earthquake when I was in Nevada.

The problem I have with statements like the above as hearsay is that it now is recorded for all internet time, and as people search for answer to placing rocks in the future it will be seen and taken as a fact, when in reality it is not a fact. I read it on the internet, it must be true.


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## JRW81 (Mar 14, 2017)

I can not remember not having at least one tank around growing up and have been keeping tanks myself for at least 25 years. About 15 years ago I set up an older tank that I had stored and put heavy rocks directly on the bottom glass as I've done many times before. Around a year of it being set up the bottom cracked directly under a big rock. I don't know if it was because of the rock or just from being an older tank that might have already been damaged. That's why I said I would rather be safe than sorry. I noticed other people saying the same when I was reading reviews on a tank for petsmart


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