glass size

[master_wise]

Hi,

I just started the hobby a year ago... And I have plans on upgrading my tank. I am building a tank in India. It will be made out of glass, I would opt of Acrylic but I just can't find someone to supply it or even build me the tank. Anyways, the local fish guys even though they claim they know what they are talking about don't have a clue about marine tank or spec. My question is:


What thickness glass would I use on a tank that is going to measure: 74 length x 36 width x 27 height.. And on the back glass I plan on drilling two 1 1\2 inch hole about 1 inch apart and 1 inch from the top and sides.
The local fish guys are say 12 mm but something just does not feel right about that and I not looking to be sitting in 300 gal of salt water.

[adnup]

Dont know about the glass but make sure with the bulk heads you take into account the size of the flange when spacing the holes. I think the general rule is atleast the width of the hole apart and away from the edges

[ambaratur]

Well the GARF tank calculator says it would need 1/2 inch which is actually 12.7 mm.

Material = Glass
Tank Height = 27"
Tank Width = 36"
Tank Length = 74 "
Glass Thickness = 1/2"
Approximate Gallons = 311


And adnup is right about the spacing of the bulkheads. You don't want them too close to each other or too close to the edge of the glass.

Not just to have them fit - but you want to make sure they do not structurally weaken the glass itself.

[master_wise]

Thanks for the speedy replies guys...

What is the GARF that you used....

And opinion on bulk head size on a tank this size... I figured an inch and half was good... thanks for warning me about the positioning of the holes that did not even occur to me...

[onetrickpony]

http://www.fnzas.org.nz/uploads/media/GlassThicknessCE_02.xls

[master_wise]

I know the website(http://www.garf.org/tank/buildtank.asp) mentions using 1/2 inch glass... But in the description it mention only fresh water.... Would the extra added weight of the salt in the water be a need for increasing the glas thickness... And also al the tanks(glass) that I have seen in India are all glued onto the bottom glass... but here they are glued onto the sided... Any opinion... I personally feel that gluing to the sides would be weaker becasue more chance of the seams just tearing apart then the bootom of the tank falling out... considering that the tank is going to be resting on soemthing...

[ambaratur]

Hmm... good points - I really don't have any good answers. I just know the garf site is a good resource. Sorry I can't help more here.

I think one of the reasons that the tanks rest on their sides here is that it may be easier to spread the weight out. If you get a pressure point on the bottom of a glass tank it can rupture. However - I am sure that there are methods for both types of construction that work.

I also think there are custom built glass tanks here that rest directly on the bottom - I think Melev has one if I remember right.

Good luck with the research.

[GARFVolunteer]

The section where you saw the fresh water description was for leak testing the tank only.

There are 2 way to build a glass tank. One with the front, back and side panels resting in the bottom panel. The other method has the weight of the tank being on the front, back and sides with the bottom being elevated sandwiched in between like the GARF calculator shows. Either method is perfectly acceptable and both are used by the major aquarium manufacturers. I personally prefer the GARF method because I like to build my stands with a solid top.

Thanks,

Scott

[master_wise]

Actually, My apologies... I meant to say that the side peices rest on the bottom glass and the front and back are both glued to the bottom... I seems to have to best of both... Thanks for all the help...

Sagar

[Pbrown3701]

Salt does not make the total volume weigh any more than freshwater. Consider that when you add the salt, you are displacing that much water. Now consider a 6 gal bucket of salt vs a 6 gal bucket of water - the water weighs more.

[ChemE]

<a href=showthread.php?s=&postid=7370994#post7370994 target=_blank>Originally posted</a> by Pbrown3701
Salt does not make the total volume weigh any more than freshwater. Consider that when you add the salt, you are displacing that much water. Now consider a 6 gal bucket of salt vs a 6 gal bucket of water - the water weighs more.

Not quite. Volumes are not always additive. There are cases when 1 gallon of A mixed with 50 gallons of B does not yield 51 gallons. This is such a case. The ions in the salt mix fit in between the water molecules thus making the final mixture more dense than water. This is why we shoot for a specific gravity of 1.02 to 1.025 while the specific gravity of pure water is 1.0.

So the real answer is that salt water adds 2.0%-2.5% to the total weight which is insignificant.

[Pbrown3701]

ahh - you're right. It's been many years since inorganic chemistry - guess i should have used the ole' common sense approach and considered the densities...