Acrylic/Glass thickness calculator

SuperNinja

Plecostomus
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Apr 30, 2014
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Hi everyone i’m working on the early stages of concrete tank build. It would be poured in place with a 4” overlap all the way around the viewing windows. Overall tank dimensions would be 18’ long x6’ deep and 5’ tall. It would have two equally spaced 4x8 acrylic panels. Just trying to figure out what size I would need thickness wise. Can’t seem to find any calculators out there and not finding much in the archives. Let me know your thoughts.

If you need more info let me know. This is early stages of planning i’m discussing with another member. Trying to document this to be the most thorough build of all time. Thank you!
 
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MultipleTankSyndrome

Giant Snakehead
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Based on the weight of the water in the tank (approx. 15300 kg), I'd estimate 32 mm as the thickness.
My 473 liter tank (therefore 473 kg of water) has glass 10 mm thick, and the cubic root of 15300/473 is about 3.2.
Hope this helps!
 

M1A1

Piranha
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Jun 10, 2013
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What is the depth of the water at the bottom of the acrylic panel? This is the critical dimension. Volume or weight of the water doesn't mean anything on it's own.

If the water depth at the bottom of the panels is 48" then estimate acrylic thickness 48mm or round up to nearest standard size, 2".

If the water depth at the bottom of the panels is 60" then estimate 68mm, 2.75" or 3".

 
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SuperNinja

Plecostomus
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The bottom of the acrylic would be about 6” from the bottom of the tank as well as the top. So that would put the bottom of the panel down. Here is a crude drawing since i’m probably doing a horrible job explaining.

drawing not to scale

image.jpg
 
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M1A1

Piranha
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So 54" water depth, you're probably still looking at 2.25" or 2.5" acrylic.
 

wednesday13

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1” acrylic will support 4’ height in 4’x4’ sections…. U can get away with maybe 1.5”-2” acrylic if u run a front support/division to cut ur 4’x8’ panels down… will save u alot of money that way… if not, as others have suggested ud need at-least 2”-2.5” minimum for ur proposed dimensions. 3” would probably be “ideal” at 5-6’ water height.
 

SuperNinja

Plecostomus
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Apr 30, 2014
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1” acrylic will support 4’ height in 4’x4’ sections…. U can get away with maybe 1.5”-2” acrylic if u run a front support/division to cut ur 4’x8’ panels down… will save u alot of money that way… if not, as others have suggested ud need at-least 2”-2.5” minimum for ur proposed dimensions. 3” would probably be “ideal” at 5-6’ water height.
so If i cut these down and did 4 panels each 4’x4’ spaced them out evenly i’d be safe with 2”?

or if i made the tank to where it was only 48” high total depth would that make 2” acrylic work? If i was to go with 2 4x8 sheets.
 

wednesday13

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so If i cut these down and did 4 panels each 4’x4’ spaced them out evenly i’d be safe with 2”?

or if i made the tank to where it was only 48” high total depth would that make 2” acrylic work? If i was to go with 2 4x8 sheets.
i think so yes… u can still use the full 4’x8’ sheet just need a vertical brace to cut the spans to 4’ lenghts. That way ur still only sealing in 2 windows instead of 4… the height is always the main factor for glass/acrylic thickness. If u go with 4’ total tank height 2” would b plenty even for a full 4’x8’ sheet. I guess ur debate now is cut the height to 4’ or push the limits a bit with a vertical center brace on ur windows to go 5’-6’ lol… ?… its always a bit hard to guess how material will handle the pressure on DIY builds also as calculators are often rated for free standing tanks. DIY style can have alot more bracing and support to hold the glass in place. With the right bracing/supports u can go 8’ tall with 1” even. It will bow but it wont fail IMO… the material thickness in ur case will come down to bowing. If ur O.K. With a bit of bowing u can save some money on the thinner material… if thats something that will bother u down the road, spend more for the thicker material. There is also a debate of whether or not windows up off the bottom need to be rated to the full tank height or just the height its supporting. Im sure someone will comment with an actual tank calculator thickness u can kinda go off of. Then think out ur budget and bracing and how to suit it best to ur needs. If money is not a worry, always go with the thickest material u can afford. If its a budget type build, bracing and cutting ur window spans to 4’ lengths to curb bowing can save alot of money.
 
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fishdance

Redtail Catfish
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Jan 30, 2007
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The good news is technology has come a long way in recent years so you are spoilt for choice. The bad news is there is a lot to choose from. Suggest you look at swim pool companies and information as most pools have viewing panels now.

I built a large concrete tank (circa 100,000L) with steel and glass viewing panes (2m water depth). Choose the right recipe of concrete. Very dense mix (42Mpa+) which is waterproof, with crystalline additive (waterproof) and painted membrane (waterproof). The tank design becomes more important once you have decided how to build. Formwork type is another huge discussion area. On your desired depth, I would use bottom drains, self cleaning circulation, rounded corners, a back or side drop internal filter so you can use airlifts. (Pump driven water will emulsify soft solids making water clarity harder and operating costs higher). Look towards koi pond concepts for tank design.

If you use a steel frame to hold your glass/acrylic panes you will strengthen the build, reduce the pane thickness, reduce the overlap required and minimise concrete edge chips. As well as reducing blind spots around the viewing panes that fish will gravitate towards. If you do use a steel frame, make that part of the concrete pour so you don't need to fasten and waterproof the steel to concrete. If your fussy, you can design a frame that sits flush with the inside concrete wall so fish don't scrape and injure themselves.

I would not recommend acrylic but it's a personal choice. Acrylic is more flexible so you need thicker to stop bowing. Or smaller size panels which is your personal choice. Glass technology is constantly improving. Tempered glass, with hydroscopic laminates was my choice. You can have triple or quadruple laminate on thinner glass to achieve overall thickness if cost is a concern. Some laminates (interlayers) are better suited than others but easy to waterproof the edges if using a steel frame.

Since we are discussing structural considerations, don't underestimate the compression pressure wave a large fish can generate in a bigger tank. A large pacu zooming up to glass then rapidly turning can easily create pressure much higher than 2m water depth.

If this is your dream tank, don't let costs ruin the overall effect and lifetime of pleasure you seek. Similarly, have another look at your dimensions to decide if it's really big enough.

YouTube has some nice concrete aquarium builds.
 
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