8'x4'x30" = 600 gal. How thick?

[TampaReefer79]

I'm looking at a used tank that is 8'x4'x30" for 600 gallons and is made with 3/4 inch acrylic...which is most likely actually .71 or something like that. I've been getting some mixed reviews regarding whether or not this tank can and will support water for years to come. Some think I'm in for a disaster should I purchase and fill it. What do you think?

The top is one 8' panel that is glued to all 4 sides and has 2 holes cut out for lighting, as opposed to strips across the top for bracing. The seams don't have bubbles and haven't started turning white. It was originally setup with 2 75 gallon surge tanks which I will not do. I would run it with a closed loop and some Tunze's/Vortech's.

Regardless I thought this would be a good spot to find out what people think about 3/4" acrylic on a tank this large. Not sure if it matters in your opinion, but it was made by [violation].

Thanks!

P.S. The owner of a well respected acrylic shop said that it should be ok as long as the top is braced well (with one sheet of acrylic) and the seams don't have bubbles or have turned white. Another well respected LFS owner is DEAD SET against the tank. He said he wouldn't have it in his house or in his store even if it was given to him. :hmm3:

So I just have to decide if I want to take the 'risk'...or is it not a risk? Please help me debate.

 

[TampaReefer79]

:spin2:

 

[Nanook]

One of our fellow moderators here had a beautiful tank built by James at www.envisionacrylics.com and it was 6ft x 4ft x 30in. If memory serves, James recommended using 1.25" acrylic on the sides or the tank would bow. We did perimeter bracing on this tank with no cross bracing. Personally, I would be very, very leary of a tank of those dimensions in only 3/4" acrylic. Sure, it might hold, but what kind of peace of mind do you want to have with 600g of saltwater and thousands of dollars of livestock???

If it sounds too good to be true, then it probably is.

 

[bullitr]

if this help my 435 gallon tank (96x36x29) will be made out of 3/4" thick acrylic all around but with a very well thought off cross bracing .

 

[camaroboy8691]

this is the tank in question .

here is the top . it is 1 peice and also 3/4 thick . i will be posting a few pics of the top seams . they are clear as day

 

[camaroboy8691]

this is looking down from through the top into the blacked out portion of the tank . what you see is the hole where the bulkhead went into it and visually looking throught the acrylic into the bottom sheet . its that clear

 

[camaroboy8691]

this pic is of one of the corners , its hard to see but there is alittle bit where the glue when it was being made tweaked the acylic but the joint is clear as day

 

[camaroboy8691]

this is the same corner as above but looking from the side .

 

[camaroboy8691]

i would also like to add to this thread , yes its a 600 gal tank . but that size is completly filled . the tank size is 96x48x30 this computed to gals is 598 gals , but thats the outside of the tank . inside measurments are roughly 94.5 x 46.5 x28.5 so that comes out to approx 542 gals of water inside the tank totally filled . now there is a trapazoidal over flow which displaces some water . but here is the kicker . from the bottom of the inside of the tank to the bottom of the over flow teeth is approx 26" so if you fill this tank up it will only hold 494 gals of water before it over flows .

so enstially figuring out the exact volume of this tank makes it alot less than a 600 gal tank . which may be the reason why the manufacturer says 3/4 is ok ?

anyways . my brain hurts now from calculating that all . time for a break . lol

 

[TampaReefer79]

i would also like to add to this thread , yes its a 600 gal tank . but that size is completly filled . the tank size is 96x48x30 this computed to gals is 598 gals , but thats the outside of the tank . inside measurments are roughly 94.5 x 46.5 x28.5 so that comes out to approx 542 gals of water inside the tank totally filled . now there is a trapazoidal over flow which displaces some water . but here is the kicker . from the bottom of the inside of the tank to the bottom of the over flow teeth is approx 26" so if you fill this tank up it will only hold 494 gals of water before it over flows .

so enstially figuring out the exact volume of this tank makes it alot less than a 600 gal tank . which may be the reason why the manufacturer says 3/4 is ok ?

anyways . my brain hurts now from calculating that all . time for a break . lol

Don't forget that a few hundred pounds of live rock will displace a lot of water too...but the amount of water that WILL be in the tank will have an awful lot of pressure. Then take into account that Dave used to rush 1500 lbs into the tank over a 5 second period every minute... lol

 

[Acrylics]

IMO the tank appears to be structurally sound, albeit a bit underbuilt, esp if wavemakers or surges are used which tend to beat on tanks a bit more and generally shorten the lifespan of the tank. As it is, the tank will hold water just fine, I'd have no worries about that. I'd personally have a problem placing two 75 gallon surges on it, but aside from that - no issues that I can see.

FWIW; "industry standard" for this tank is 3/4". Panel thickness requirement is determined by the height and span on a "per panel" basis, so this tank is in line with industry standards. Volume of the tank doesn't play into the equation at all - it literally is all about height, span, and deflection tolerance for any given bracing scheme. Even 1/2" acrylic would hold water on this size - wouldn't be pretty, but would hold water.

FWIW part II; These days, 3/4" acrylic pretty much is .708". Years ago, most acrylic mfrs went metric so calling out 3/4" acrylic will get usually get you 18mm acrylic or .708"

Nanook,
The tank you were referring to had no crossbracing and the perimeter flange was nowhere near as wide as this is, hence the 1.25" that was spec'd out

HTH,
James