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I'm planning to build an aquarium - 50 gallons. I estimate that it'll weight 550 pounds. It would be in the top of a cabinet... but the top of that cabinet is a suspended glass. It's similiar to this one but without the drawers.

to this one

How can i reinforce it using just glass, so it won't break when my aquarium gets filled with water, fishes, rocks and so on ?

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The point loads you're talking about introducing here scare me. Aquariums put all their weight on the outside edge (by the edge framing) and proper aquarium stands transfer that load vertically directly to the floor. This design will create lateral loads and high stress corner points. BAD idea. –  The Evil Greebo Sep 6 '12 at 14:27
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With a quick back-of-the-envelope calcuation, I came up with 0.3633" thick for tempered glass, or 0.7416" thick for regular glass if you've got a perfectly uniform load on a 1' x 4' piece of glass bearing 550 lbs, supported only at the ends. This is with absolutely no safety factor either! (The required thickness will be significantly reduced if you support it in the center, but I can't tell from the picture how the entertainment center is set up.) –  Doresoom Sep 6 '12 at 17:13
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You also need to take into account the weight of the tank itself, the gravel, and anything else that you put into the tank, not only the water. A fully loaded 50 gallon tank can weigh up to 800 pounds, forget the glass, can the cabinet support that much weight? –  Gunner Sep 6 '12 at 23:42
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This makes me want to giggle. Glass, really really bad idea! Filled just will water not grave is 625 lbs get a cabinet made for the tank –  user14511 Aug 13 '13 at 0:19
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3 Answers

up vote 6 down vote accepted

This sounds like a bad plan. 550 pounds (or more, likely) is just way too much weight to try to hack something together. Even if you put a support in the middle, then you need to make sure it's perfectly balanced or you're going to crack the aquarium at the pivot point — the glass tank is going to be very unforgiving of an uneven surface.

Plus, think of the enormous problem if your tank does crack or fall over. 50 gallons of water could cause a huge amount of damage. Make sure your homeowner's policy includes flood coverage that would pay for this if you do try it!

Just get a stand that's build to hold an aquarium. It will probably be cheaper than buying a massive piece of tempered glass.

(Although I strongly discourage this idea, if you are committed I would suggest that you carefully test your contraption. Get a bunch of bricks, bags of gravel, etc. that weigh a little more than you're expecting. E.g. if you think the tank will end up being 600 lbs all told, gather up 800 lbs of materials and stack it in the tank. Leave it for a few days. Jump on the floor. Throw a pillow at it. Knock on the glass. Lean on the cabinet. If it's going to collapse, you want to find out before you have all the water and fish in there.)

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The Evil Greebo is correct. Glass is simply not that strong. So if you intend to do this despite the warnings you will get, I'd find a glass shop that can supply you with a replacement glass top that is thick enough so it WILL support the design load. They may suggest the use of tempered glass. The problem is, thicker glass will be fairly expensive, especially tempered glass.

Another option, coming at this as a woodworker, is a way that is commonly used to strengthen long shelves that are supported at the ends. Essentially one would laminate a second piece of wood along the front and rear edges of the shelf. This creates a beam that is stronger than the single thickness of shelf material, with less deflection. One would probably need to use an epoxy to form the lamination. Again, a glass shop would tell you if this was feasible or worth the expense.

Finally, an additional support in the center of a shelf will vastly increase the load it can support, compared to a beam that is supported only at the ends.

To be honest, I'd go for an appropriate thickness of tempered glass. It won't be cheap. Even better is to avoid the glass top completely. Remember that failure in this case is an extreme event. Lots of water, dead fish, big bills to clean it all up.

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+1 Thanks for the complete answer, I'll just this open to see other ideas (if someone else posts something)... –  woliveirajr Sep 6 '12 at 16:59
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You could build a sub-top using a torsion box design or something similar that will support the weight adequately. It could be designed so it is tapered at the front edge. Then lay a thinner pieces of glass over that and at least from the front it would have a look similar to the concept above.

It seems to me that if there is any deflection of the top at all it is going to lead to eventual failure of the aquarium itself. Whatever material you use I would pay close attention to the deflection expected in the middle of the shelf.

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