# Glass too thin for tank?



## Jbakewell (25 Oct 2019)

Hi everyone

I’ve just bought a 60x30x30 tank with 4mm glass panes. While I think the manufacturer is trustworthy, I’ve been a bit concerned as to whether the glass might be too thin for the tank size. 

Also, my filter is a canister filter that hangs on the side on the tank (see image). I’m going to put a thick sponge underneath it to take weight off the braces, but I’m not sure it will be safe given the glass width when everything is up and running. 

Thoughts? Has anyone here used a 4mm glass tank before of a similar size? 

Thanks!


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## alto (25 Oct 2019)

ADA uses 6mm glass, as does UNS for their 60U (60 x 36 x 36cm)

4mm rimless - be very careful that it’s level in all directions, that you’ve used a suitable anti-vibration mat (similar to ADA Garden Mat), and never accidentally knock it ... and inspect the silicone seals closely 

What’s the Manufacturer warranty?


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## Fisher2007 (25 Oct 2019)

My gut feeling is that 4mm is too thin and I would have expected 6mm.  See link though, this is done in 5mm so 4mm might just be doable. Got to be on the very edge of safe though surely

https://www.aquariumgardens.co.uk/optiwhite-60-by-ag-glass-aquarium-60x30x36cm-3385-p.asp


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## zozo (25 Oct 2019)

4mm is a standard thickness for this size, for example, the Hagen / Marina Solid glass tanks 54 Litre sold in many pet stores. Pretty common around Europe. Fluval is actually also from Hagen Group.

I've used it for many years and never had a structural problem with it. And the tank still stands in the garden today.


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## lazybones51 (25 Oct 2019)

Fisher2007 said:


> My gut feeling is that 4mm is too thin and I would have expected 6mm.  See link though, this is done in 5mm so 4mm might just be doable. Got to be on the very edge of safe though surely
> 
> https://www.aquariumgardens.co.uk/optiwhite-60-by-ag-glass-aquarium-60x30x36cm-3385-p.asp


I have seen that 5mm optiwhite tank in AG and there's a slight bow in the front, which you don't get in a 6mm ADA. I imagine 4mm is going to bow a fair amount over 600mm.


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## zozo (25 Oct 2019)

lazybones51 said:


> I have seen that 5mm optiwhite tank in AG and there's a slight bow in the front, which you don't get in a 6mm ADA. I imagine 4mm is going to bow a fair amount over 600mm.



Yes, it does about 10 to 20mm total in the centre. But that's no structural problem. I also went 6mm on a 90x35 cm tank and this bows similarly.

And once went for 125cm x 20 cm with 4mm glass and the centre bow was over 30mm over a length at 125cm it looks awful but still not a structural problem.

Glass is pretty flexible under equal pressure, what it doesn't like is point pressure and contortion. 

See this: In aquarium building, a safety factor is used related to glass thickness pressure resistance.

Commonly SF 2.5 is considered safe.



SF4 is Very Safe.



SF8 is equaly very safe.




If for your peace of mind SF8 is very safer than go 6mm 

http://theaquatools.com/building-your-aquarium/


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## Edvet (25 Oct 2019)

60x30x30 cm @ 4 mm


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## Costa (25 Oct 2019)

Do you see how it's stressed around the middle of the glass?

6mm should be the absolute minimum


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## Edvet (25 Oct 2019)

Not stressed just a bit "fluid".


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## Jbakewell (25 Oct 2019)

zozo said:


> 4mm is a standard thickness for this size, for example, the Hagen / Marina Solid glass tanks 54 Litre sold in many pet stores. Pretty common around Europe. Fluval is actually also from Hagen Group.
> 
> I've used it for many years and never had a structural problem with it. And the tank still stands in the garden today.



This is reassuring. I guess it wouldn’t be standard if even a minority of people with these tanks reported problems


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## Zeus. (25 Oct 2019)

Remember reading about Clive's  700l tank having a bow in it also


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## Jbakewell (25 Oct 2019)

zozo said:


> Yes, it does about 10 to 20mm total in the centre. But that's no structural problem. I also went 6mm on a 90x35 cm tank and this bows similarly.
> 
> And once went for 125cm x 20 cm with 4mm glass and the centre bow was over 30mm over a length at 125cm it looks awful but still not a structural problem.
> 
> ...



If these calculations are valid it looks like It will be ok? I was concerned 4mm would be on the very edge of safe, but if it is indeed considered ‘very safe’ than returning it for 6mm would be overkill no? 

Would be a bit frustrated if it bows a lot though. It’s an optiwhite tank and I’d hate for the view to become distorted


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## Jbakewell (25 Oct 2019)

Edvet said:


> 60x30x30 cm @ 4 mm
> View attachment 128540



Hmm are you this is safe? Also does the bowing depend on the quality of the seals?


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## Aqua sobriquet (25 Oct 2019)

I’d go on the safe side and use 10mm ...


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## zozo (25 Oct 2019)

Jbakewell said:


> If these calculations are valid it looks like It will be ok? I was concerned 4mm would be on the very edge of safe, but if it is indeed considered ‘very safe’ than returning it for 6mm would be overkill no?
> 
> Would be a bit frustrated if it bows a lot though. It’s an optiwhite tank and I’d hate for the view to become distorted



For the safety, it ain't an issue the rest is personal aesthetical value and choice.  I'm also not sure if 6mm will not bow at all. Visually it still might look straight, but once you place a perfect flat ruler over the glass you still might see a little bow. That's for an owner of such a tank to try and confirm or deny. My gut says it still bulges a little.

From experience, i know that even a 25mm Euro brace on a bowing tank and it didn't prevent it from bulging out. And a euro brace is a 25mm wide additional strip sealed perpendicular to the top of the front and back panel entire length. It reduced bowing for 75% but it still bows a little.



Jbakewell said:


> Also does the bowing depend on the quality of the seals?



No not at all, the bowing is in the flexibility of the glass panel related to its height. Since the pressure of the water relates to water column height, this means 30cm water gives more outward pressure than 20cm water. This you can see to take 10cm water out of your 30cm tank and see it bow less.

Like the example bellow shows, if the tank gets taller the glass needs to be thicker.


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## Jbakewell (25 Oct 2019)

zozo said:


> For the safety, it ain't an issue the rest is personal aesthetical value and choice.  I'm also not sure if 6mm will not bow at all. Visually it still might look straight, but once you place a perfect flat ruler over the glass you still might see a little bow. That's for an owner of such a tank to try and confirm or deny. My gut says it still bulges a little.
> 
> From experience, i know that even a 25mm Euro brace on a bowing tank and it didn't prevent it from bulging out. And a euro brace is a 25mm wide additional strip sealed perpendicular to the top of the front and back panel entire length. It reduced bowing for 75% but it still bows a little.
> 
> ...



I think I’ll see how it fares for a couple of months, and if it ends up bowing like crazy I’ll add a centre brace in the new year. Thanks for the advice


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