Can Rocks Crack Aquarium Glass?

Hello,
I have a 240l Juwel Rio tank with 8 neon tetras and 6 panda cories.
In my tank, it has 3 rocks with a piece of driftwood ontop to make a cave thingy.
However, I am worried that the rocks may strain or crack the glass bottom of the aquarium. I don't know if it's laying on sand or not because I think I put a thin layer of sand, then the rocks, then more sand. I want to check if there's sand under the rock but I don't wanna disturb the fish or cause everything to move. I've also read about putting eggcrates before the substrate to evenly distribute the weight but it's too late now and I regret it.
Any help please?
Thanks

 

Unlikely. I have probably hundreds of pounds of rock on one end of my 75 and it's been holding strong for years.

 

If you drop it harshly it could crack the aquarium, but I doubt it will do anything if it's just sitting there.

 

I've used all varieties of rocks in my tanks for years and as said above unless you really drop one they should be fine. If it's already in there and you didn't crack it I would highly doubt it could cause damage now. I myself have had rocks slip and fall countless times while putting them in place and I have even dropped a couple on the way in. Never caused damage. I've never dropped them directly onto the glass... There's always been a layer of some kind of substrate down to "cushion" their fall.

 

a hard blow, sharp localized impact, that will definitely crack a glass tank. however, back in high school I had this debate with a friend, so in my folks backyard I kept stacking brick after brick in some crappy throw away tank and the bottom glass did not break under the weight of several feet of a jenga stacked brick tower. after that, being stupid we took everything out and jumped up and down in it, then of course it broke. in short you can fill cement in those tanks to the brI'm and theoretically it should hold indefinitely.

 

So is the eggcrate thing paranoia? I read that a heavy stone over sand can cause pressure points on the glass, eventually causing it to crack. I remember putting large, heaavy stones in a turtle enclosure with no issues. I'm pretty dubious too.

 

You should never put heavy stone on to of substrate. The stones go first and the substrate surrounds it. Fish like to excavate and any movement of a heavy stone would be an issue.

As far as the weight issue, it's a non issue. The bottom pane of glass can support tremendous pressure and localized stress. The manufacturers wellbeing depends on the ability to handle whatever the consumer throws as it.

 

Technically, if you put a boulder in an mbuna tank and they toppled it, it could break the glass. But a meteor hit would do the same, and in years on forums and with keeping fish that dig and move rocks, I have never heard of a rock breaking a tank or a meteor hitting one.
A lot of manufacturers use tempered glass on the bottom (worth checking for if you ever plan to drill a tank for filtration purposes). They are pretty strong.

 

A few days ago, I accidentally dropped a 3kg rock into one of my tanks - it fell through about 40cm of water.

It looks like there's a tiny chip where it landed, but there are no cracks.

 

the bottom pane is tempered glass, you're not supposed to put rock on top of sand for the reason MikeRad89 stated. I can't tell you how many people I know have had cichlids topple holey rock, but the bottom never broke, it was always a side panel.



edit; so I just used a tempered glass calculator and apparently a standard 20 gallon long can support 1960 lbs

 

Hey guys! Thanks for all the help!
Do you think that the fish like neon tetras, panda cories, BN pleco, guppies, gouramis, Bolivian rams and other tetras can cause rocks to move since some of my medium sized rocks are on top of the sand?

 

Hey guys! Thanks for all the help!
Do you think that the fish like neon tetras, panda cories, BN pleco, guppies, gouramis, Bolivian rams and other tetras can cause rocks to move since some of my medium sized rocks are on top of the sand?

Probably going to be, no.

The only way the could move if the fish was purposely trying to nudge it around. Or if their was some erratic swimming behaviors. Then I'd have to disagree with the rocks moving. I once had my betta tank have only river rocks as a substrate.

 

Probably going to be, no.

The only way the could move if the fish was purposely trying to nudge it around. Or if their was some erratic swimming behaviors. Then I'd have to disagree with the rocks moving. I once had my betta tank have only river rocks as a substrate.

Thanks. Do you think if they dig under the rock, it'll cause it to lose balance and topple?

D'ya think any fish will disturb the substrate under the rocks causing them to topple or that these rocks will cause any stress/damage on glass?
Thanks for all the help guys I appreciate it

 

D'ya think any fish will disturb the substrate under the rocks causing them to topple or that these rocks will cause any stress/damage on glass?
Thanks for all the help guys I appreciate it

I highly doubt it, but would be surprised if they did.

 

as others have said, the rock directly on the glass should be fine. However, in the future I plan on putting some egg crate down under the sand and placing the rocks on it. More so for peace of mind.

 

Hello,
I have a 240l Juwel Rio tank with 8 neon tetras and 6 panda cories.
In my tank, it has 3 rocks with a piece of driftwood ontop to make a cave thingy.
However, I am worried that the rocks may strain or crack the glass bottom of the aquarium. I don't know if it's laying on sand or not because I think I put a thin layer of sand, then the rocks, then more sand. I want to check if there's sand under the rock but I don't wanna disturb the fish or cause everything to move. I've also read about putting eggcrates before the substrate to evenly distribute the weight but it's too late now and I regret it.
Any help please?
Thanks

It depends upon the amount of weight you have in total. Aquariums are made of tempered glass which will help to withstand a heavy load. However glass does have stress points. Typically in corners or along the edges when framed. The center area of a glass pane will flex. Which is why larger tanks have cross members along the bottom. The key is to evenly distribute weight to avoid putting too much stress in one area. Typically, the recommendation for sand or gravel substrate is approx. 1.25-1.5lb per gallon. The reason the recommendation for adding egg crate is that it helps to spread the load evenly across the bottom of the tank. So, Ideally you would want one piece of egg crate to span the entire length and width of the bottom of the tank. This creates a better, more uniform base for weight distribution.

As long as your rocks aren't too large and heavy, plus the weight of your substrate, etc. you should be good. Though I do not recommend placing them directly on the glass because of the stress points they create.

 

What do you guys think I could do right now to prevent this problem?

 

The rocks in your picture look pretty steady to me