Longtime lurker here, and I’m having trouble finding information I need on the net.
Figured I would ask the world’s largest repository of Those In The Know TM. I want to build a custom acrylic aquarium. I will be using a steel frame, so corner pressure/weakness is not a huge concern. However the tank will be a vertical tank (MUCH taller than a typical tank) so being that the water pressure should be a function of its height, I need help calculating the neccessary thickness of the acrylic.
The tank will be 3 feet wide, 3 feet deep, and 7 feet high. (Kinda like a phone booth. The edges and sides will be a rigid steel frame. I need to know how thick to make the 3 foot by 7 foot sheets to withstand the pressure from 470 gallons of water. I’ve seen guides for building tanks 3 foot HIGH, and 7 feet WIDE, but even though they hold the same amount of water, the pressure on mine will be much higher, right? Any help, insight would be appreciated! Thanks in advance.
With no knowledge specifically of acrylic and its strengh I doubt that you will actually break the sides of the acrylic. I would wager that you need to worry more about the seam strength. Either way, your 3 foot deep tank would have a pressure of 2300 lbf/ft^2 and your 7 foot deep tank would have a pressure of 2553 lbf/ft^2. I doubt it will make very much of a difference.
Thats completely wrong unless you live in a vacuum. The right pressures are 187.3 lbf/ft^2 and 436.8 lbf/ft^2. I still doubt that you are going to crack the acrylic.
Of what thickness? I’m SURE that if I use 1/4 inch thickness that the very small tanks (10 gallon) use, that it WILL crack. Some of the larger tanks were using half inch, or 5/8 inch thickness for 30 inch heights. But if the pressure on an eight foot heighth is so much greater, will that still suffice?
Do you really need (or just want) a fish tank of that height?
Just what is the application. Personal or business/commercial installation?
Money no object?
Contact a plastics supplier, such as: Piedmont Plastics, 1-900-331-7898. They should be able to give some advice.
You should have a certified engineering design if located in a business enviorment for insurance/liability purposes.
On more serious terms, the likely answer to Dewey Finn’s question is ‘no’.
Filled with water, you have 62.4 lb/ft[sup]3[/sup] * 7 ft = 440 psf on that floor.
Most houses have a live load rating of 40 psf, so you aren’t going to put that anywhere inside without some serious extra floor support.
Indoor tanks of 7 feet high are really pretty rare, most likely for this reason.
And as treis said, the seams are of far more concern than the wall materials. The moment due to the variation in pressure over height seems a likely problem with all-glass construction. A steel frame may be the best bet.
I used to design and install custom aquariums. The posters who mention floor weight are correct: within the industry you’re always hearing of some rookie who put too tall a tank too far away from a support and crashed the damn thing through the floor. The biggest tank I ever did, we had an engineer install supports in the basement belowe the tank.
Couple things to keep in mind with the tank you envision: cracking acrylic isn’t so much an issue as bowing. Make it thick enough so it doesn’t look like a pregnant woman when you view it from the side.
Also, how will you reach the bottom of the tank for maintenance? If there will be fish in it, you will get algae, and you’ll need to devise a way to scrub the insides of the tank seven feet down. Thick acrylic makes those magnet things iffy, and with a tank that tall it’ll be hard to get any decent leverage to scrub from above. Also, acrylic scratches over time, so you’ll need to be able to scrub carefully.
Substrate is an issue too. Gravel will require cleaning. I hope you drill the bottom of the tank and filter it that way. It will make maintenance easier.
Finally, the lower and wider the tank, the better the oxygen exchange rate. Therefore the taller and narrower it is, the less oxygen concentration you’re likely to have. A tall narrow tank will comfortably house far fewer fish than a low wide one. Also, aesthetically, fish swimming around horizontally makes visual sense; fish swimming up and down against the sides of the tank has a slightly jarring, unnatural appearance. This may be a minor consideration, but there it is.
Listen to "lissener,’ the voice of experience.
Get some real aquarium engineering help if you must have the tank described.
As is a doityourself job it wil end up with money spent and unsatisfactory results.
In simple english: If you don’t know how DON’T.
Thanks for the advice. And to clarify, the tank won’t be used in a traditional sense. I’m actually recreating an illusion which Houdini performed: “The Water Torture Cell”.
In further refining the design, I see that the tank will only be 30" wide on the inside, and without a person in it, the water only needs to rise about 57". Which means about 1850 lbs. of water (plus frame and magician, little over a ton). The tank will be on a steel square wider than the tank, and YES the floor will support it. I have some experience in illusion building, but having never constructed a tank, I’m doing some preliminary research.
Lissener , Have you ever worked with Lexan (polycarbonate)? I see that its 250 times stronger than glass, thicker than 1/2" is sometimes bulletproof. Acrylic is only 10 times stronger. Looks a little pricier, but I want this thing to hold the water, and be relatively safe (besides the drowning bit!) I found the tensile strength for Lexan listed, Treis would you mind converting that answer to PSI?
The tank will have support cross braces to help prevent bowing. Link
Now we can understand what you want to do.
This AM on GMA/NBC they showed the new GA Aquarium. Transparent walls 20 ft. hi. 60 ft. wide. and 2 ft. thick.
Once a man is inside in the water the pressures etc. will be just as if it were filled with all water to the air/water interface with a man present.
My guess is that 3/4" Lexan woud be adequate but you should consult with a plastics supplier/expert.
No, sorry. I mostly used glass, when I was building the aquarium myself, unless it was too big. In those cases, I contracted it out, because the nature of the join/seal takes some experience and finesse. I’d done it with smaller tanks, but with bigger tanks I deferred to experience.
