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Thread: 75 gallon rebuild gone wrong need help

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    DIYFK member Raiderfaithful's Avatar


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    75 gallon rebuild gone wrong need help

    Hey everyone names Zach I'm new to this forum. I recently got inspired to rebuild an old 75 gallon aquarium. While disassembling I broke the bottom pane of glass. The entire tank was made with 3/8" plate glass. My question is can i use a 1/4" piece of tempered glass that is the same size as the old bottom to replace it. This would save me about $70 at my local glass shop!

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    DIYFK member Meep's Avatar


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    That is a loaded question, can you sure, is it a good idea, maybe not but maybe so... Was the original tank bottom tempered? Aqueon says there 75 bottom is tempered ( http://www.aqueonproducts.com/assets/012/23821.pdf ) and other brands might be as well... You can technically use thinner glass if it's fully supported, aka use a thin Yogo type mat (or foam) under the entire bottom on a solid topped plywood stand... That way the bottom won't bow or flex, the thin Yoga mat or foam sheet will assure you don't have pressure points on the glass...

    FYI, don't be penny wise and dollar silly, watch Craigslist and you can probably pick up another 75 gallon for under $40, likely less or even free if it has a broken side or leaks...

    Also are you sure the glass shop is going to cut some 1/4" glass and then temper it for you for that much less than a 3/8" piece, do they even have a tempering oven on site or are they going to send it out and incur more cost? Generally tempered glass is 4-5 times the cost of regular glass, and 3/8" glass is not 4-5 times the cost of 1/4", so I can't personally see how the claimed savings on 1/4" tempered adds up... A completely 'stock' (pre-made table top) tempered 1/4" 48x18 piece of glass is about $125 - $150... You might want to shop around, they probably just don't want to deal with the heavier 3/8" and are socking it to you with $$$ for the inconvenience... But, as I said when you can get used 75s for under $40 pretty regularly, I caution you on spending too much on just a piece of replacement glass...

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    DIYFK member Raiderfaithful's Avatar


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    Click here to enlarge Originally Posted by Meep Click here to enlarge
    That is a loaded question, can you sure, is it a good idea, maybe not but maybe so... Was the original tank bottom tempered? Aqueon and other brands might be as well... You can technically use thinner glass if it's fully supported, aka use a thin Yogo type mat (or foam) under the entire bottom on a solid topped plywood stand... That way the bottom won't bow or flex, the thin Yoga mat or foam sheet will assure you don't have pressure points on the glass...

    FYI, don't be penny wise and dollar silly, watch Craigslist and you can probably pick up another 75 gallon for under $40, likely less or even free if it has a broken side or leaks...

    Also are you sure the glass shop is going to cut some 1/4" glass and then temper it for you for that much less than a 3/8" piece, do they even have a tempering oven on site or are they going to send it out and incur more cost? Generally tempered glass is 4-5 times the cost of regular glass, and 3/8" glass is not 4-5 times the cost of 1/4", so I can't personally see how the claimed savings on 1/4" tempered adds up... A completely 'stock' (pre-made table top) tempered 1/4" 48x18 piece of glass is about $125 - $150... You might want to shop around, they probably just don't want to deal with the heavier 3/8" and are socking it to you with $$$ for the inconvenience... But, as I said when you can get used 75s for under $40 pretty regularly, I caution you on spending too much on just a piece of replacement glass...
    Thanks for the response. They said a 48x18 piece at 1/4" tempered is about $45 and a 3/8" plate is about $115. I was planning on putting it on a metal stand with a thin gauge rolled steel top (Father runs a metal fabricating shop) with some sort of foam underneath. My biggest thing is does it really make a difference that the bottom panel is an 1/8" thinner than the sides if the method I'm using is the one where all 4 side sit on top of the bottom pane?

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    DIYFK member Meep's Avatar


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    As I said shop around, you are paying more for a single piece of 'undersized' glass then you will likely pay for an entire used tank that has the proper sized glass... Also again call another glass shop or two, I just looked at the prices for a local glass shop online in my area and they quote online $6 sqft for 3/8" plate glass, so at 18x48 that is only $38.40...

    Standard metal stands only support the edges of the tank, if you go thinner you will most definitely need to support the entire bottom and then cross your fingers that it works... IMO thin gauge rolled steel isn't going to cut it (of course the all depends on you definition of thin) as it will still have plenty of it's own flex, instead use a sheet of 3/4" plywood if you insist on doing this... And yes the thinner bottom does make a big deal, the bottom is under the most force, and when you work the load and force numbers the bottom should technically be the 'thickest' piece of glass, not the 'thinnest'...

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    DIYFK member Raiderfaithful's Avatar


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    2x3 or 3x3 steel tubing at 4 foot long with two center supports with 14-16 gauge steel should have 0 flex

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    DIYFK member Raiderfaithful's Avatar


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    Also I'm in Phoenix so by all means if someone knows of a cheaper place to buy 3/8 plate glass please let me know

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    DIYFK member Meep's Avatar


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    Click here to enlarge Originally Posted by Raiderfaithful Click here to enlarge
    2x3 or 3x3 steel tubing at 4 foot long with two center supports with 14-16 gauge steel should have 0 flex
    For one, you did not specify how the stand was to built or is to be built, so my assumption was a factory metal stand that is usually just 1" angle with no center supports, and fully dependent upon the tank being trimmed, if you go thinner on the bottom glass you can't use a normal trim as the bottom needs full support... I also do not consider 14 gauge sheet to be a thin gauge that is about twice the thickness of car body panels and even new integrated unibody car frames are thinner at 16 gauge... Now that you specified it will be an incredibly overbuilt stand with 2x3 or 3x3 tubing, have 2 center braces and use 14 gauge steel that is a different story, assuming you can get the top dead on flat on that build, so that there are no high low pressure points on the glass bottom it might work...

    That said I still would not drop down to 1/4" personally, just not worth the risk of failure IMO... About maybe 30 years ago all the major tank manufactures started to cut back cost by using thinner glass, and plastic trim rings, today's tanks are already less robust than they used to be, and IMO if the manufactures could get away with thinner and cheaper glass on the bottom like you want to do they would be doing it...

    The thing to remember is that although tempered glass is a lot stronger, it still bows more than the un-tempered and thicker glass and this is the issue you face when using it for fish tanks, the corner seams on a tank will not allow for much bowing without failure...

    Also I'm in Phoenix so by all means if someone knows of a cheaper place to buy 3/8 plate glass please let me know

    Another option, there is slight variations in how tank manufactures assemble tanks and the exact dimensions they use, and it can vary by year as well, but you might be able to find an older 55 gallon that had the thicker 3/8" un-tempered front/back glass and re-purpose the front/back of that 55 as the bottom of your 75... If you did find a 55 with suitable glass that was long enough it should not cost more than a few bucks to have it trimmed down to the proper width to use as the 75's bottom at a local glass shop... The local pet store by me that sells used equipment sells 55s for $20, sometimes $10 or $15 if they are dirty and ugly, so it's a lot of glass for that price if you can find something comparable... Also don't be afraid to low ball the guys on Craigslist, way too many of them believe their used tanks are made of gold for some reason... Petco regularly runs their $1 per gallon tank sale up to 55 gallons, yet there is no shortage of people wanting upwards of $2-3 a gallon for their dirty used tank on Craigslist, sometimes the seller need to be leveled with...

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