Tempered glass in an aquarium

I have the opportunity to buy a 75 gallon aquarium with either a tempered glass bottom or non-tempered glass. The 48" x 18" bottom pane of glass is 1/4" thick (guessing here) but the non-tempered glass is at least 3/8" and maybe even 1/2" thick. I know that tempered glass is much better for impact resistance for small objects at a high velocity. Here is my question:

Which of the two tanks would be less likely to break/crack if a rather large (40 lbs?) rock was dropped a rather short distance (18"?) onto the bottom pane of glass.


Mon, 10/01/2005 - 14:23

If you are going to set your tank up as saltwater tank I would get the tank that is not tempered. If you end up going to a reef tank you will want to be able to drill a hole in the bottom for a better filter. If not, go with the tempered. Don't forget you will have gravel or crushed coral on the bottom, to absorb the impact. Hope this helps.
Liberty Glass and Metal

Guest User
Tue, 11/01/2005 - 03:29

Okay, I have to ask. Why do you want to drop a 40 lb rock in your aquarium? Also if you put a piece of 1/4 lexan in the bottom of the tank on top of the tempered the lexan would take all of the punishment and protect the glass.

Guest User
Tue, 25/01/2005 - 00:35

African cichlids are very aggressive fish that need lots of rockwork so the sub-dominant fish can hide from the tank bully. So it is not uncommon to have a 40 lb rock in a 75 gallon aquarium. It is not a salt-water tank and I do not plan to have it drilled.

I believe that Aquarium manufacturers use tempered glass only in the bottom and only on tanks no larger than 75 gallons but I don't know the reason for this. One friend told me that the less expensive tempered glass tank is actually much better able to resist impact loads from dropped rocks (which is why I need a new tank). Another friend felt that I should pay a little extra money for the non-tempered glass tank because the glass is considerably thicker and less likely to crack should I prove stupid enough to make the same mistake twice.

I guess without knowing the thickness of each, there is no way to answer my question.


Guest User
Thu, 27/01/2005 - 16:22


As a general rule tempered glass of the same thick is about 6 times stronger than annealed glass. However, when it breaks it shatters completely.

If you have expensive fish in your aquarium use the annealed glass. If it breaks and you are not around (asleep or at work, etc.) you will later discover an aquarium with a slow leak with your expensive fish in the bottom with possibly some water still in the aquarium. Chances are the fish will still be alive.

If you have the one with tempered glass and it breaks, the glass falls completely out - along with your gravel, water and most importantly your fish. So within three or four minutes your fish are dead and your total investment with it.

The previous answer about drilling is also pertinent because "serious fish people" often change the fish in their aquariums and need to add holes for pumps, etc.


Guest User
Fri, 28/01/2005 - 01:43

In my opinion, I think the tempered glass would be less likely broken. Because it depends on the feature of the tempered glass.

Firstly, you should know that what

Guest User
Fri, 28/01/2005 - 12:50

"As it was broken, the tempered glass disintegrates into small cubical fragments relatively harmless to human body." Broken tempered glass is just as sharp as any other broken glass it is just smaller. Also temperature variations (in the tempering process) can affect the size and shape of the broken glass. Properly tempered glass will break into small sharp fragments the size relative to the thickness of the glass. Improperly tempered it will break into long and sharp shards. HTH Lee

Guest User
Mon, 21/06/2010 - 07:57

Why dont you select Laminated Glass for your base?
even If the Glass breaks it will still hold its place and there would be only water leakage.

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