# Acrylic cover, thickness recommendation.



## GlenD (20 Oct 2019)

So I have a 90 cm X 45 cm aquarium.  I purchased 2 X 45 cm x 4 mm thick acrylic sheets to act as a cover. 

These worked fine for about a week and then they started to bow, with LED lighting and no real heat in the area.

 I want to replace these with one single sheet, with a central hole for feeding access.  What is the recommended thickness for the acrylic covers so sagging/bowing is limited.  I don’t really want to go for a glass cover as there is a few odd cutouts that I need to do.


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## Aqua sobriquet (20 Oct 2019)

I’ve got a 31cm cube with a 6mm thick PETG cover supported near the four corners and it still has a slight bow in it. You can get 8mm and 10mm thick but it may cut down the light too much? I went for PETG because it’s not brittle and easily broken like Acrylic.


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## Edvet (20 Oct 2019)

Most will sag eventually, maybe use a smaller glaspane under  an acrylic sheet which covers the cutouts?


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## dean (20 Oct 2019)

I believe it’s about the type of acrylic you use 
There’s two types 
Extruded and cast 
Extruded is used for almost everything as it’s cheaper to produce but it warps in high humidity 
Cast acrylic is used to make aquariums 
It’s a lot more expensive even than glass that’s one reason you don’t find many acrylic aquariums on the market unless they are a shape that isn’t possible in glass such as a large sphere 

Polycarbonate is also available in clear in different thicknesses 
I’ve never used it or know if it’s warps or not 
See what your favourite search engine says 

Let us know too 


Sent from my iPhone using Tapatalk


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## Aqua sobriquet (20 Oct 2019)

Clear Polycarbonate is expensive and if you look at it edge on it has a purple tint. I used to use it quite a bit years ago for things that needed to be tough.


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## The Accidental Aquascaper (20 Oct 2019)

Hi Glen

Page 4 of my journal shows the lid I had made - https://www.ukaps.org/forum/threads/the-accidental-aquascape.56871/page-4
The tanks footprint is 100cm x 35cm. The lid thickness is 8mm, but I wish I went for 10mm, as it does bow slightly.
I've designed it so you can use it any way round, so I flip it over once the bowing is obvious.


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## alto (20 Oct 2019)

Why not just use glass 
(If you follow the ADA cover glass dimensions, then you can use the ADA clips - which are far less visible than the alternate versions I’ve seen)

LED lights can get very hot depending on type, cooling etc


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## The Accidental Aquascaper (20 Oct 2019)

alto said:


> Why not just use glass



I considered the same thing, as it's by far the superior material to use. However, it's got some downsides that made it a non-starter for me.
The shape of the cut-outs I want are quite complex, so it would be quite expensive to have that made. But the main reason is, I would eventually smash it by accident.
Then there's the option to have sliding glass, but that's never going to look good and I would probably smash that too


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## tam (20 Oct 2019)

You could put so braces on or flip the lid over twice a week.


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## zozo (21 Oct 2019)

The problem with acrylic is it becomes pliable at rather low temps at 80°C and it can be pressed into a mould.

That is also the issue with extruded acrylic, it is pressed into a mould and therefore contains a lot of tension after its cured. Then if it's without bracing and exposed to fluctuating temperatures it will release this tension and warp into different directions.

Casted acrylic has less tension because it's manufactured/cast at a higher temp instead.
But still exposed to gravity and fluctuating temps 25°C + it will not warp but sag if not braced properly.

Casted acrylic is more expensive than glass and as said still needs to be braced.


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## GlenD (8 Nov 2019)

dean said:


> I believe it’s about the type of acrylic you use
> There’s two types
> Extruded and cast
> Extruded is used for almost everything as it’s cheaper to produce but it warps in high humidity
> ...



Well I have gone for 8 mm clear cast acrylic. With eight support clips to give support all the way round. We will see.

PS Cost around £48, made to size with a 25mm feeding hole.


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