Strength of glass

[iamborg]

I am planning to setup a 40G breeder standard Aqueon tank as a reef tank.
The stand I have is a 40G petco metal stand.

The stand is "hollow" on the top, and the tank is only resting on the edges.

If I put sand [40 lbs] and rocks [40 lbs] + the weight of the water, wont the
bottom of the glass tank break under such a large amount of weight?

Also the rocks are not evenly distributed, wont there be pressure points
on the bottom of the glass?

Please advise. thanks.

 

[Tastee]

I would place a layer of plywood on top of the stand, then a layer of foam and finally the tank. I am not an engineer but would expect 9mm/3/8" would suffice. I would personally use 12mm/1/2" to be safe.


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[mcgyvr]

The tanks and stand are designed to not break under typical usage..
What you describe falls under typical usage..
You do not need to do anything special.

The bottom piece of glass is not resting on the ground and the only thing touching is the black trim piece..

Putting a piece of plywood will make no difference at all. The bottom glass will still be floating off the plywood and the trim perimeter is still the only contact with the plywood surface.. Nothing changes..

 

[billdogg]

The tanks and stand are designed to not break under typical usage..
What you describe falls under typical usage..
You do not need to do anything special.

The bottom piece of glass is not resting on the ground and the only thing touching is the black trim piece..

Putting a piece of plywood will make no difference at all. The bottom glass will still be floating off the plywood and the trim perimeter is still the only contact with the plywood surface.. Nothing changes..

^^^this^^^

 

[Tastee]

The tanks and stand are designed to not break under typical usage..
What you describe falls under typical usage..
You do not need to do anything special.

The bottom piece of glass is not resting on the ground and the only thing touching is the black trim piece..

Putting a piece of plywood will make no difference at all. The bottom glass will still be floating off the plywood and the trim perimeter is still the only contact with the plywood surface.. Nothing changes..

Apologies for the bad advice, thanks for the correction [MENTION=38412]mcgyvr[/MENTION] & [MENTION=188122]billdogg[/MENTION]



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[billdogg]

No worries! It is a common misconception. There are two ways to make a tank. You can have a floating bottom. 99% of "standard" tanks with plastic trim are made this way. The other option is to use the bottom pane of glass as the platform on which the 4 sides rest. I would guess that most (if not all) rimless tanks are made in this manner.

When the bottom is floating, all the weight rests on the perimeter of the tank and only the edges (especially the corners) need support. Many people use a piece of plywood underneath them anyway if for no other reason than it will block the light into the sump area if you are going bare bottomed or use a shallow sandbed that might allow some light through. What you DON'T want to do is put anything that is compressible under a floating bottom because if it compresses enough it can press up on the bottom glass and potentially cause the seal to fail. Although some still go this route due to uneven stand tops, it is generally not advised. The reason is that although it will, indeed, compress and appear to even the load, it won't necessarily prevent pressure points that can damage the tank at some point down the road.

On the other hand, if the tank does not have a floating bottom, it will require support across it's entire surface so that the weight of the tank is spread evenly. This is when a solid surface like plywood is mandatory. It is also a good time to consider a thin sheet of Styrofoam or or slightly compressible material is a great idea. It will allow for whatever slight imperfections to be compensated for and prevent pressure points that can easily crack the bottom glass.

HTH!

 

[mcgyvr]

No worries! It is a common misconception. There are two ways to make a tank. You can have a floating bottom. 99% of "standard" tanks with plastic trim are made this way. The other option is to use the bottom pane of glass as the platform on which the 4 sides rest. I would guess that most (if not all) rimless tanks are made in this manner.

When the bottom is floating, all the weight rests on the perimeter of the tank and only the edges (especially the corners) need support. Many people use a piece of plywood underneath them anyway if for no other reason than it will block the light into the sump area if you are going bare bottomed or use a shallow sandbed that might allow some light through. What you DON'T want to do is put anything that is compressible under a floating bottom because if it compresses enough it can press up on the bottom glass and potentially cause the seal to fail. Although some still go this route due to uneven stand tops, it is generally not advised. The reason is that although it will, indeed, compress and appear to even the load, it won't necessarily prevent pressure points that can damage the tank at some point down the road.

On the other hand, if the tank does not have a floating bottom, it will require support across it's entire surface so that the weight of the tank is spread evenly. This is when a solid surface like plywood is mandatory. It is also a good time to consider a thin sheet of Styrofoam or or slightly compressible material is a great idea. It will allow for whatever slight imperfections to be compensated for and prevent pressure points that can easily crack the bottom glass.

HTH!

^^^this^^^ [MENTION=51392]Billdog[/MENTION].. :wavehand::lmao:

I don't even consider it "bad advice".. There is really no harm in doing what you proposed so its not "bad".. Just not needed..

 

[iamborg]

Thank you for the clarification and advise.

This is my first try with a large standard rim tank.
My previous tanks were all rimless and small [8G, 24G], and all of them
have flat supported stand under the bottom; so I was worried.

Thanks again.

 

[mcgyvr]

Yep..
Often times "rimless" and other "non-floating" tanks require full support as well as a manufacturer specified padding to maintain integrity as well as warranty of the tank..