4 X 15 X 18 tank glass thinkness opinion

I have a freind who i'm getting into the hobby and he's decided to getting a 4 X 15' X 18' standard size 4ft tank ..

He's determined to get it made up with 10mm glass instead of the standard 6mm..

Is this an overkill or worth paying triple the price (about $120au dollars v's around $500au for the same tank in 10mm glass)

I used this guide when building my tank:

Is it 18' deep? If so 6 mm is minimum IMO. What about 8mm or laminated glass it's not as good as float glass for constant load stresses but it's a bit cheaper for thicker glass when it's made of 2 thinner peices stuck together. Laminated glass has the advantage of holding together when broken so you may have time to avert disaster if your home and the tank fails. I have an old 18' deep tank that is 6mm float/annealed glass (20 years old or so and still going) For a 15 inch deep tank 6mm would be no worries. Has your friend had a tank fail before? I guess it would be once bitten many times shy with a failing reef tank.

What a mess.

Trying to convert to US measure to make it easier here. If I am reading this correctly, 10mm = 3/8 6mm = 1/4 It is about a 55 gal tank. Most tanks here that you buy do use the 3/8' glass (10mm) for that size. It may be ok with the thinner glass but also may be more susceptible to bowing and seam seperation. Not sure though. Maybe someone with better glass knowledge can help.

Glenn www.aquarium-stands.com