# used bow front tank



## kd5exp (Mar 21, 2014)

I just got a used tank real cheap (36.50) and a peice of the bottom trim is missing. I have a couple idea on how to make a trim peice. Anybody got some suggestions on how to do this? I can't seem to ID this tank so it must be an old one. Lady I got this from said she thought it was a 39 gal and I posted the dimensions on here and was suggested it was a 46 gal. I put it out on my picnic table and filled it and no leaks. I will retest it when I get done with it and make sure I don't create a leak. Thanks Gene :roll:


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## triscuit (May 6, 2005)

It's a good idea to replace it with something, but my best suggestion is to get some angle iron at the hardware store and silicone it in place.


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## sumthinfishy (Jan 26, 2013)

a "piece" of anything is of no benefit other than cosmetics. the trim on the top and bottom of tank are continuous piece for a reason. the help with the structural integrity of the tank. if u add a piece without reconnecting to the rest of the trim somehow, then aside from the appearance of the tank, this piece will do nothing. if u were to use angle iron as suggested, then u will need to find a way to attach to the rest of the trim, not just silicon in place


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## BillD (May 17, 2005)

The trim on the bottom is of no structural benefit. If the bottom of the tank isn't the lowest part, the trim will protect the edges of the glass sides. So, if the sides are on the bottom, you don't need any trim. You should set the tank on a piece of styrofoam.


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## sumthinfishy (Jan 26, 2013)

in an aquarium pressure is equally distributed throughout entire glass structure when full. there is just as much force pushing outward on the bottom edges as there is on top. if the pressure wasnt distributed evenly then glass would shatter. take a 55 gallon with a center brace for example. the bottom trim is identical with a center brace as well. if it wasnt supporting any pressure dont u think the manufacturer would save themselve a ton of money in material cost by not having center supprt on bottom?


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## triscuit (May 6, 2005)

sumthinfishy said:


> in an aquarium pressure is equally distributed throughout entire glass structure when full. there is just as much force pushing outward on the bottom edges as there is on top. if the pressure wasnt distributed evenly then glass would shatter.


Nope. 
http://www.engineeringtoolbox.com/hydro ... _1632.html


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## sumthinfishy (Jan 26, 2013)

i have run my own tests on various tanks with and without rims. i have seen the difference a piece of trim can make on top and bottom first hand. the op can make there own decisions based on the different advice that they have received. i never give comments or advice based on articles someone else has written. i will only give advice based on my experiences and what i've seen first hand. will i read articles and learn from them? yes i wil, but will not advise anyone on how to do anything that i havent experienced myself


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## triscuit (May 6, 2005)

sumthinfishy said:


> i have run my own tests on various tanks with and without rims. i have seen the difference a piece of trim can make on top and bottom first hand. the op can make there own decisions based on the different advice that they have received. i never give comments or advice based on articles someone else has written. i will only give advice based on my experiences and what i've seen first hand. will i read articles and learn from them? yes i wil, but will not advise anyone on how to do anything that i havent experienced myself


Sounds like a wise policy. However, a basic understanding of hydrostatics might help you interpret and share your experiences in this case.


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## triscuit (May 6, 2005)

BillD said:


> The trim on the bottom is of no structural benefit. If the bottom of the tank isn't the lowest part, the trim will protect the edges of the glass sides. So, if the sides are on the bottom, you don't need any trim. You should set the tank on a piece of styrofoam.


The trim usually prevents the glass from bowing, and protects the silicone seal from shearing-type stress.


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## sumthinfishy (Jan 26, 2013)

all i need to know is how to read a tape measure. which i do. that tape measure was able to show me how much a glass tank will bow without trim on it. i know its basic thinking and i dont have a phd, but sometimes common sense is our best friend. bowing tank = water on floor


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## smitty814 (Sep 27, 2012)

Now I'm curious. How much does the bottom of a tank bow?


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## mambee (Apr 13, 2003)

I personally would never screw around with used tanks, especially ones that are missing pieces. I live in an apartment on the second floor and already have nightmares about one of my tanks busting.

I hear that some of the big box stores have $1/gallon sales, so you can buy a brand new tank for basically the same price.


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## sumthinfishy (Jan 26, 2013)

smitty814 said:


> Now I'm curious. How much does the bottom of a tank bow?


my 75 with braces removed bowed over an inch on top and bottom when full


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## smitty814 (Sep 27, 2012)

sumthinfishy said:


> my 75 with braces removed bowed over an inch on top and bottom when full


No pictures......didn't happen. :fish:


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## sumthinfishy (Jan 26, 2013)

ok. believe me or dont believe me. it has no bearing on my life. this was two years ago. i didnt know that i would need evidence down the road. do it yourself if u wanna see. i have no reason to lie.


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## fmueller (Jan 11, 2004)

smitty814 said:


> No pictures......didn't happen. :fish:


+1

sumthinfishy - if you aren't kidding, there is something seriously wrong with your tape measure! A 75G will experience total structural failure long before bowing an inch at the top - let alone at the bottom! But I agree with you that common sense is our best friend, so I can save myself the trouble of destroying a 75G to prove an obvious point.


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## sumthinfishy (Jan 26, 2013)

ok. believe what u want. this isnt the first time that u guys "think" u know everything and i'm sure it wont be the last. your right i have made this whole thing up because i have nothing better to do with my time then make up stories for people i dont know. good day. do u feel better?


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## sumthinfishy (Jan 26, 2013)

Just remember that the 1 inch measurement is a measurement of overall bowling front and back not just 1 inch out the front. it Bows in both directions just the same because as I stated pressure is equal


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## sumthinfishy (Jan 26, 2013)

triscuit said:


> BillD said:
> 
> 
> > The trim on the bottom is of no structural benefit. If the bottom of the tank isn't the lowest part, the trim will protect the edges of the glass sides. So, if the sides are on the bottom, you don't need any trim. You should set the tank on a piece of styrofoam.
> ...


this is my basis for getting involved in this thread. triscuit agrees that trim prevents bowing and shearing at slicon right? triscuit was was the one that suggested a "piece" and i disagreed that a piece would have ti complete trim and be connected. triscuit then turns around and aggrees. now u are all arguing with me on haw far it bows? serious?


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## smitty814 (Sep 27, 2012)

sumthinfishy said:


> Just remember that the 1 inch measurement is a measurement of overall bowling front and back not just 1 inch out the front. it Bows in both directions just the same because as I stated pressure is equal


In order for the bottom section of the front back and sides of an aquarium to bow the bottom would have to flex up or down. Either direction is unlikely. :thumb:


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## sumthinfishy (Jan 26, 2013)

not if its stretching at the seems. the glue and silicon will stretch and tear before bottom would bow upward.


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## sumthinfishy (Jan 26, 2013)

not to mention the bottom would only have to bow upward if it was a cmpletely sealed box. an aquarium is open at the top. if sides, front, and back bow out the the overall water level would just drop slightly as it spread. only in an air tight cube would bottom have to bow for the sides, back, and front to bow. nice try though.


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## smitty814 (Sep 27, 2012)

The bottom will not bow up. It cannont bow down as long as the silicon seals hold, the front, back and sides will go nowhere at the bottom of the tank. Only without support at the top will the top front, back or sides bow.
Being full of water the tank is air tight. otherwise it would leak.
And that's all I will say on that. =D>


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## sumthinfishy (Jan 26, 2013)

i realize its air tight and will remain as such as water level lowers and sides bow out. and it can bow at bottom without bottom doing anything if the seams stretch to compensate for bow until they finally tear. i dont know what part of this u dont understand. the seems are the week link in the chain. i'm gonna wrap this up by saying that regardless of whether u believe me or not, my opinion on this matter, based on my experience regarding this matter, is that the top and bottom frame are critical to the integrity of the overall tank. my advice to the op is to replace broke frame with a one piece frame just like it was originally manufactured with. especially where its a bowfront tank to begin with. thank you and good night


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## fmueller (Jan 11, 2004)

I suggest we all stay civil and focus on answering the OP's question rather than turning this and other threads into a battle of egos. Without pointing fingers, I'd say whenever you have three post in a row, you should question your motives, because you would seem to be monopolizing a thread.

It might also be good to go back to the basics every one in a while. Denying that the pressure exerted by a fluid depends upon the depth of the fluid is like claiming that water runs up the hill in your neck of the woods. Chances that anybody will buy this are slim, and it's a basic principle of psychology that you reduce your credibility by making statements that are so obviously false.

Now taking my own advice and looking again at the OP's question about a medium sized tank with a bottom trim piece missing, I would recommend replacing it even if just for cosmetic reasons. The pressure at the bottom of the tank is actually greater than at the top, but loosing a trim piece or brace at the bottom is far less critical than at the top, because the bottom glass already acts as a very efficient brace, while there is no top glass! Obviously the best solution would be the one that closest mimics the design used by the manufacturer - if there was a bottom center brace to begin with, it would be nice to have one again. Failing that, something like an angle iron siliconed to the entire bottom edge of the tank could make a very efficient side brace. The iron would resist bowing and thereby take any stress off the glass. Many modern tanks use side braces at the top instead of center braces. I can't see why this should not work at the bottom.


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## sumthinfishy (Jan 26, 2013)

your statement regarding angle iron to contain the bow is false. the iron is harder than the glass and will remain straight as the bow in center pushes outward causing spacing in the corner. the only way that angle iron would contain bow is if it was connected to side trim, which in turn is connected to rear trim.

_Post edited by moderator to remove personal attacks and off topic content._


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## sumthinfishy (Jan 26, 2013)

"denying that the pressure exerted by a fluid depends on depth" I NEVER DID!


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## fmueller (Jan 11, 2004)

sumthinfishy said:


> your statement regarding angle iron to contain the bow is false. the iron is harder than the glass and will remain straight as the bow in center pushes outward causing spacing in the corner. the only way that angle iron would contain bow is if it was connected to side trim, which in turn is connected to rear trim.


I have asked you politely to stay on topic and refrain from personal attacks. I have edited your post to be in compliance with my request.

Iron is actually softer than glass - Moh's hardness 4 compared to 5.5 - but that is quite irrelevant for the question at hand. The point is that if the iron is attached to the whole length of the edge, it will prevent the glass from bowing, and this would be much stronger than having the iron only connected to the side trim at the end.

The concept is the same as in this glass tank, which is side braced at the top. Note how the side braces are not connected to the side glass on either end.


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## fmueller (Jan 11, 2004)

sumthinfishy said:


> "denying that the pressure exerted by a fluid depends on depth" I NEVER DID!


Sure you did:



sumthinfishy said:


> in an aquarium pressure is equally distributed throughout entire glass structure when full. there is just as much force pushing outward on the bottom edges as there is on top. if the pressure wasnt distributed evenly then glass would shatter.


If there was "just as much force pushing outward on the bottom edges as there is on top" then the pressure exerted by water would have to independent of depth. Since it is dependent on depth, the "force pushing outward on the bottom edges" is greater than it is on top.


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## sumthinfishy (Jan 26, 2013)

_Post edited by moderator to remove personal attacks and off topic content._


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## sumthinfishy (Jan 26, 2013)

sorry. last post was posted prior to me reading your explanation of depth. i was wrong there. u are right


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## sumthinfishy (Jan 26, 2013)

i leave this discussion with my original opinion and advice. trim is essential to overall integrity of tank. i would make the repair the trim so it was back to the way it was when it left manufacturer.


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## BillD (May 17, 2005)

Having built a few tanks, which are trimless, the bottom trim is not necessary, in a sides on bottom construction. It isn't technically essential even with a floating bottom type of construction, but I don't like the idea of the tank sitting on the thin panes of glass or the bottom being hung by silicone. the corners are very vulnerable if they get bumped when moving or placing the tank. Depending on the thickness of the glass and the length of the tank, some form of bracing may be required in the centre to prevent bowing. Alternatively what is called euro bracing, where there is a brace over the length of the glass, as in the picture posted above, can be used.
As to trimmed tanks having centre braces on the bottom, that is because t is easier to only make one trim piece. If you have two moulds you would make two pieces rather than make two different ones. The material cost between the two is negligible, while the cost of moulds isn't. There are still tanks being built without centre bracing or even one piece trim The local Big Al's has a number of 6', 120 gal tanks which have no brace and use add on trim (4 pieces). These tanks have been built this way for years and are still built this way. Keep in mind that using a one piece moulded trim allows for quick and easy assembly.
For those of you who would only buy new tanks, keep doing so. Most of my tanks came as leakers, including a bunch from Big Al's that were bought new, sprung leaks, and were returned to the store. None have leaked since I repaired them.
This type of discussion is worthwhile, as we can see, that aside from differences of opinion, there are questionable "facts" being bandied about.


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