# Perspex Lids



## Tomp91 (21 May 2020)

Hi All,

I bought some perspex sheets to use as lids in 3mm thickness, they have already started to flex in the middle after a few days as is unsupported, just wondering if anyone knows what thickness if any can support its own weight properly.

They are only  32cmx28cm didn't think it would be a an issue.


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## chinwag (21 May 2020)

Can't really suggest a thickness but I always think of perspex as being quite flexible but also quite brittle at that sort of thickness.

You could always look at acrylic as well - there's a lot of places on ebay now that will cut to size both acrylic and perspex in different thicknesses.


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## Tomp91 (22 May 2020)

I'll take a look at acrylic, thanks!


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## Tomp91 (22 May 2020)

I think Perspex is acrylic, Perspex just being a brand name. Ebay posts certainly have both in the title! ha


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## nigel bentley (22 May 2020)

Hi Tony, 
When you say 'lid', do you mean between the water and light or the actual tank cover above the light? 

I'm asking as I was considering perspex for a tank cover. The wooden cover on my Seabray tank is warping and needs replacing. This is due to condensation as I  removed the glass sliding lids  to enhance light. Rather foolish possibly. 

I was considering using perspex, but after hearing your problem, I may try hardboard. Obviously if this is going under the light it wouldnt work
All the best 
Nigel


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## Tomp91 (22 May 2020)

Its between the water and light. According to the website its clearer than glass so shouldn't cause any issues blocking light. My Monte Carlo is still pearling anyway!

I think I am going to try again with a thicker piece, it still only has the slight dip it got almost straight away so I reckon 5 or 7mm would have been OK.

Shame I bought three!

I also bought "glass look" which I think just means they add a green edge but its a lot more green than even my cheap glass so I recommend going with clear!


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## Aqua sobriquet (22 May 2020)

I’m using 6mm PETG on one of my Nano’s and it’s not bad.


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## nigel bentley (22 May 2020)

I should imagine thicker would be best. Think I will go for at least 6 mm with a brace in the middle and both ends. 

I love Monte Carlos carpet plants BTW. 
Staysafr
Nigel


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## milla (22 May 2020)

At this size why not just use glass?


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## zozo (22 May 2020)

What you need to look out for is GS Cast acrylic, this type is much more stable.. What's regularly available in the hardware store is XT extruded acrylic, the production process is a lot cheaper but it leaves the finished material with a lot of internal tension and stress. Then as soon as it is warmed up it starts releasing tension and stress and will warp.

Even GS acrylic might bend a bit if it's not properly supported and gets warm.  

Whatever type acrylic you use it is best to create a frame around it, then for example if you use 6mm acrylic sheet, frame all around it in 8x1mm aluminium U profile. Since it is 1mm thick Alu profile the gap inside the U is 6mm. The acrylic will fit snugly in, then use a dot of sealant to keep it in place. 

This way it is unable to bend.


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## Tomp91 (22 May 2020)

milla said:


> At this size why not just use glass?



I will have a look at glass I would prefer that, not sure why I haven't, I suppose I assumed it would be expensive.


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## Tomp91 (22 May 2020)

as I need 3 the glass would be about £80 compared to the £20 I spent on perspex from a quick check. Worth it I think.... shame i didn't do that first.

Saying that though the 3 tanks were only £90 all in....so maybe its not.


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## milla (22 May 2020)

Tomp91 said:


> as I need 3 the glass would be about £80 compared to the £20 I spent on perspex from a quick check. Worth it I think.... shame i didn't do that first.
> 
> Saying that though the 3 tanks were only £90 all in....so maybe its not.



I pay £6 per sq ft for 6mm with safty edges at my local glaziers / glass cutters  So 3 would be about £18 - £20

float glass. opti white would be more expensive i expect


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## Tomp91 (23 May 2020)

That's sounds more like it I'll shop around!


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