Broken Tank Support

eug

An article that talks about both longitudinal and cross bracing on all-glass aquariums:
Aquarium Fish Tank Build Aquariums

Also another thread that shows many aquariums using this very construction, and your exact problem of it having been accidentally cracked.
http://www.wetwebmedia.com/glstkbraces.htm

eug

Sorry Rjordan, but what do you think the aquarium sealant is doing at the seams of the aquarium? Do you realize how much hydrostatic pressure the seams have to be able to support?

rjordan390

<You can easily fix it in again with silicone sealant - but remember that you will have to lower the water level to a point where the bowing is hardly occuring before you slilicone the brace back into place.>

I beg to differ.
The poster is not an aquarium builder. If DIY are getting away using sealant to hold a brace then they are pushing their luck. You might want to ask the manufacturers why they have a center brace as an integral part of their large aquariums. its true that the sealant has good holding power but because its more flexable, manufacturers feel its safer to have proper bracing and not depend on sealant to do more then its intended purpose.

rjordan390

<Sorry Rjordan, but what do you think the aquarium sealant is doing at the seams of the aquarium? Do you realize how much hydrostatic pressure the seams have to be able to support?>

The seams at the corners are the strongest part of the aquarium because of the one piece contruction of the top and bottom with a center brace on each. Most of the pressure will be on the front and rear glass. Take away the center brace and you compromise safety.

Varkolak

I've looked into building aquariums and have talked to several who have built many, most of the time the only thing holding aquariums together is the silicon - the top and bottom trim is just that, a trim for looks. I will agree that a center brace is important for tall aquariums but saying that because its made of glass its not strong enough shows a lack of knowledge. Glass braces were the standard for several companies at one point and many only went to plastic because its cheaper material. I myself have a 50-60gallon with a 3/8in glass panel in the center as the support brace and I would guarantee it to be stronger then the flimsy pieces of plastic my 150 gallon has as braces. You can easily repair your tanks glass support by lowering the water level down enough that the measurements on the ends of the tank are within 2-3mm of the measurement of the center where the brace was. Then use a razor blade to remove the old silicon, use alcohol to clean the area, then put an even bead of silicon on the rim of the glass under the lip formed by the trim. Then gently press the new panel of glass into place and hold it in place for 5-10minutes; If it is a tight fit you may not need to hold it very long. Once its secure but before the silicon finishes curing add a thin layer to seal the corners on the inside for a smooth seam. Wait at least 24hrs before returning the water level to its norm to allow the silicon to completely cure.

If you want added strength and don't trust yourself then you can add a 1/2 to 1 inch by 1/4 by the width of the panel piece of scrap glass under your brace by adding silicon to one side and gently pressing them into place snug underneath but thats really unnecessary for a tank your size unless you plan on putting a lot of weight on it (I only added braces on a shelf that holds 15-20lbs of sand in a tank).

Hope this helps you if you aren't set on making it into a frog habitat
Oh and be carefully breaking the rest of that glass brace off, it wont be easy to remove so use heavy gloves and work at it with a razor blade

eug

As far as I know, manufacturers build (or commonly used to build, as Varkolak says in the post above me) tanks in this way attaching glass center braces to the inside of the front and back panes using silicone. You are arguing that the glass brace was put in by another owner, but the poster hasn't indicated that there's any traces of another type of brace being broken/replaced, so I think it's more likely that seeing that it's an older tank, the glass brace is factory-original and if the original poster can recreate this glass brace, things should be OK. I would be veer on the side of paranoia though, and over-build the brace slightly - use thicker glass. It's important to use glass and not plexiglass, because silicone bonds permanently to glass but not to plexiglass, along with several other types of plastic. Actually ideally the brace would be put directly on the aquarium glass theoretically for this reason, but if the manufacturer chose to attach it to the plastic frame, there must be a good reason for it (obviously that particular plastic has no problem bonding to silicone) and simply re-creating the original is probably simplest and safest.

Rjordan, look up Euro-bracing for a type of tank that is very common these days, especially with tanks without a cover. Up to a certain size of tank, Euro-bracing without cross braces is another option, and those are built with pure glass longitudinal braces attached to all four sides of the aquarium using silicone. Silicone also has the advantage in being so flexible that it evens out any unevenness in the joints, which otherwise might lead to certain points of the glass receiving concentrated amounts of strain resulting in leaks/cracks/tank explosions. The way I understand it, the combination of its bonding strength and its flexibility is what makes it a good adhesive for aquarium building.

Tazman

I would highly recommend avoid using alcohol as a cleaner with a tank with fish in. If any is spilled in the tank by accident it can be deadly to fish.

Can the Original Poster post a picture of the tank to get an idea of what we are dealing with before we offer suggestions for fixes?

Depending on the thickness of glass used in the manufacture of the tank, not all tanks require bracing. my 75g tank has no bracing on it and none is required as it is made from thicker glass. The deflection when fully filled is about 1mm or less.

eug

Hmm. I think if the tank was safe without the brace, the manufacturer would not bother spending money putting one in. ;) To save on costs, tanks can be built with thinner glass PROVIDED proper bracing is put in. You can only really have it one way or another, and as I said, it doesn't make much sense that a mass-manufacturer would put in a hefty piece of glass there "just for the heck of it."

Oh but Tazman brings up a good point about removing old silcone. Alcohol doesn't do anything to dissolve silicone so don't use it, it just adds risk of killing fish as he said. Cured silicone can only be removed by scraping it off diligently with a razor blade. There may be solvents out there that can dissolve it, but again this is out of the question near fish. Make absolute sure you scrape off ALL of the old silicone because the new silicone will not bond properly to the surfaces if there's some remnants of the old silicone left on it.

Tazman

I missed the pictures earlier..oops

I really suspect that piece has been added later as it is a lot wider than most tank manufactures use for bracing. A thin strip of glass / plastic is all that is needed not a pane like piece that size.

eug

All I can say is... maybe. Hard to say without taking measurements and actually seeing if there's a problem with bowing. OP, if you're feeling adventurous and want to contribute to science, try carefully and VERY gradually filling the tank and measure the amount of bowing in the middle as you add little amounts of water - take a tape measure, measure the outside edges of the glass from back to front, and then take the same measurement in the middle. As in, add a bit of water, take a measurement, and if the bowing is still just a millimeter or two, continue adding water bit by bit. Stop adding water obviously if the bowing starts to get worrying! I don't know if there's something similar in the US, but after doing some painstaking research for my own tank, I learned that there's a German industry standard that says the glass is allowed to bow up to a maximum of 1/500 of the length of the glass - so if the front pane is 1 m long, it can bow out up to 2 mm. In my case, after removing the OEM braces like an idiot, the bowing was certainly exceeding this guideline, and so I had to DIY a good solution - now the bowing is well under this limit and I can sleep soundly at night. Oh and I'll add this was for a 30 gallon tank, much smaller than than OP's.