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The strengthening bar fell out of my tank last night in my 5ftx2ftx19inch tank. It has three spaced evenly across the top.
Nothing seemed to have happened to the tank though it still has water in it but I reduced the level in it to appx 18".
the tank is 10mm glass, is this middle bar really necessary?
I don't know much about the properties of glass, if it was going to break would it have broken by now or does it take a while for the stress to crak the glass?
I am wondering because the access was a bit limited with it in and now is great.
Here is a picture of the new span.


Thanks
Matt

I'm no expert but last time this happend to my 4 foot I managed to support it with broom handles braced against a wall while I re siliconed the brace.

The bow in the glass was very alarming.

I had a 3 foot tank on one of my ranks that the brace parted on, it didnt look too bad so I put off doing anything about it and a few days later the tank seperated at one end for about half way down, didnt loose any fish but as the rack was on a ballcocked sump system it pumped a huge amount of water through my garage as it tried to replace the escapeing water.

Since then my rule is brace allways...

Matt,
Jools and I have talked about this at length. US-made tanks never have strengthening or stress bars while nearly all European tanks have them. I really do not understand what purpose they serve except to set lights on. Glass bows slightly on larger tanks. It is "normal." I would be willing to bet you could take out all the bars and the tank would be fine... just like every US-made tank. I have a 36" X 19" X 12" with no stress bar that says "Made in 1972" on the bottom (it was a gift from a friend). It has no stress bars and has moved with me for the last 16 years and been set up and running on three continents. It has never leaked.
-Shane

once I leaned on the stressbar of a 150 * 50 * 60 stressbar - it burst, and the top of the front window came almost 2 cm out.

needless to say I emptied the tank, managed it within an hour, and replaced it

Perhaps US made tanks are made from thicker glass, but thinner glass, and a stress bar would result in much cheaper tanks - with the same risks involved

Decorating my 12 mm glass 4 meter tank, I hit one of the stressbars with a 1 kg rock - and went through it

It is mend, now. No rist with this tank (2800 liters)

Shane wrote:Matt,
Jools and I have talked about this at length. US-made tanks never have strengthening or stress bars while nearly all European tanks have them. I really do not understand what purpose they serve except to set lights on. Glass bows slightly on larger tanks. It is "normal." I would be willing to bet you could take out all the bars and the tank would be fine... just like every US-made tank. I have a 36" X 19" X 12" with no stress bar that says "Made in 1972" on the bottom (it was a gift from a friend). It has no stress bars and has moved with me for the last 16 years and been set up and running on three continents. It has never leaked.
-Shane

I live in the states and our tanks have stress bars too. My 55gal 4' has one and the 125gal 6' long I'm looking to buy has two.

I have built a few hundred all glass aquariums over the years. The largest was a five foot 90 gallon.

My designs were developed in the early '70's. I always built them with full length stiffener strips on the long sides then bonded a cross piece across the center glued to both sides and the under sides of the stiffing strips. I guess today, this is called "Eurostyle".

I would recommend adding the full length strips and replacing the center cross bar; it is the most important brace on a long tank. It might work without the cross brace for awhile, but eventually the tank is likely to fail catastrophically. The longitudinal braces are essential; a simple butt joint or just gluing it to the top panes will not have sufficient strength to withstand the shear and tensile stresses. Be sure to do this with the tank empty and clean. I always used the cross strip for any tank 3 feet or more in length. Normally I use a 4-inch cross brace on a 3-feet. I used a 6-inch wide cross brace on tanks longer than 3-feet.

One of my favorite designs that I could use 1/4-inch plate glass on was 16 X 16X X 48 inches; 53 gallons. The other was 48 X 16 X 18H inches; 60 gallons.

When I had a fish shop, I built 100 25 gallon QT tanks where all new shipments were held. I usually bought fish in box lots. These tanks were made of 3/16-inch glass with only lengthwise strips and no cross braces.
They were 30L X 16W X 12H inches. I also used to keep my breeding pairs of discus in these.

I think in part it depends on the thickness of the glass. Most of the cheap tanks on the market have stressbars and thing glass, and large tanks (5 feet plus) don't. Many 4 foot 90 gallon tanks don't. I have a 33 gal (36 x 18" tall) which has a stressbar, and a 55 gal (36 x 20" tall) without. The former has 5 or 6 mm glass while the latter has 8 or 9 mm. If the tank was built with a stressbar, it was probably for a good reason - I would put the stiffening strips and the bar in for sure.

Let's keep in mind that 36 inches is less than a meter. My tankbuilder notmally starts using stressbars at 120 cm - that is 4 feet - 48 inches, 6 mm glass

I once had a 120 cm tank without them, and is was OK. The strips along the long planes were, owever, very large (8 cm instead of 4). I think that was the trick

[Mod edit: Fix apparent missing zero in the first 120 --Mats]