Glass Thickness & Rimless Conversion

onetwothree

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Joined
3 Jan 2020
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28
Location
Leeds
Hello All,

As a very new fish keeper, the first tank I purchased was 2nd hand (about 6 weeks ago or so). It's a Roma 125 in reasonably good condition, which I decided to de-rim as I prefer the look. After several hours with a very fine blade, I completely removed the top rim and silicon with no issue while leaving the bottom rim. The tank has been holding water for 6 weekish is now with no issue, with about 1.5 inches of space at the top.

I recently noticed some slight bowing in the front and back of the tank. After googling, I've read about a few people who have made this conversion with no issue. However, i'd be lying if I said the bowing doesn't concern me.

I found this tool referenced within in another thread - http://theaquatools.com/building-your-aquarium/, which seems to state that the 6mm glass is within the 'safe' range. I understand the pressure on the glass is the same as the downwards pressure on the stand (which is alot...). But, I have no idea how much force 6mm of glass and some silicon can withstand or if bowing is a sign that I'm going to walk in and find 125 litres of water in my home office.

Am I freaking out over nothing here?
 

Simon Cole

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Joined
25 Dec 2018
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469
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Buckingham
Bowing is perfectly normal.
The plastic trim had little structural benefit if any.
I've just rebuilt a 5mm 3ft tank with new bracing. It's got a huge rock resting against the back pane and supports a quad T5. It bows a bit too but is well within tolerances.

You are freaking out over nothing my friend.
 

Wookii

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13 Nov 2019
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957
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Nottingham
Did the plastic you removed have a cross brace over the middle of the aquarium, or was it just a trim around the top edge? If the latter then it's probably not an issue and was just cosmetic and to allow the fitting of the lid, but if it had an integral cross brace I'd personally be a little more concerned.

The little 60 litre tank we're currently using has a plastic top rim and brace. When the tank is empty the brace is fairly flimsy and flexible, but once the tank is filled with water the brace is stretched taught and is rock solid, which suggests to me that its taking quite a load from the pressure exerted on the glass.
 

onetwothree

Member
Joined
3 Jan 2020
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28
Location
Leeds
What thickness is the glass?

Google shows the tank being 50cm high

That's incorrect. It's 46cm from top of glass to bottom of plastic trim, so I expect around 45cm height when totally filled. This also matches with the volume of the tank (80cm*35cm*45cm = 125 litres), so I believe 45 must be the case.

Did the plastic you removed have a cross brace over the middle of the aquarium, or was it just a trim around the top edge? If the latter then it's probably not an issue and was just cosmetic and to allow the fitting of the lid, but if it had an integral cross brace I'd personally be a little more concerned.

The little 60 litre tank we're currently using has a plastic top rim and brace. When the tank is empty the brace is fairly flimsy and flexible, but once the tank is filled with water the brace is stretched taught and is rock solid, which suggests to me that its taking quite a load from the pressure exerted on the glass.

I can't actually remember to be honest - I believe there may have been a brace? I've actually decided to start running the tank with 10cm of clear space at the top. So, I'm effectively running at 98 litres (80*35*35) of water as opposed to 125. This is my first tank and I don't plan on stocking it ridiculously full, so 100ish litres is plenty. With 6mm glass, this puts me well within the stress test limits of most calculators I have found, giving me a stress rating of 4-5.

My rio 240 split a seam, there is a calculator here. At least you will know how close you are.
It split the night after I took the seam off.

https://www.easycalculation.com/measurement/aquarium-glass-thickness-calculator.php

Thanks for this. As mentioned above, I've decided to run the tank at 100 litres as opposed to 125, just to reduce the weight and be on the safe side. The bowing is reduced significantly and according to the calculator you provided and others, with the 6mm glass, puts me well within safe limits.

Watching with interest, I'm about to do the same.

Pretty easy process and looks much better. The rim on the 125 is horribly large to fix that lighting fixture in. As mentioned, I'm now running at 100 litres in stead of 125 and the bow is greatly reduced and has set my mind at ease.
 

Ricrhys

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12 Jan 2020
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12
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Aberystwyth
Pretty easy process and looks much better. The rim on the 125 is horribly large to fix that lighting fixture in. As mentioned, I'm now running at 100 litres in stead of 125 and the bow is greatly reduced and has set my mind at ease.

When I eventually get the tank set up I'd like to have some emersed plants/hardscape so running it low would work for me too.
 
Joined
10 Mar 2018
Messages
455
Location
Aylesbury
Pretty easy process and looks much better. The rim on the 125 is horribly large to fix that lighting fixture in. As mentioned, I'm now running at 100 litres in stead of 125 and the bow is greatly reduced and has set my mind at ease.

What about siliconing in place a 8mm x 25mm strip of glass along the top corner, any local window glazer should be able to cut it. Make a massive difference to it bending.
 

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