what can i do with 5mm glass??
 

how big can i go? i do have a tempered base that is 2 1/2'x 2 1/2'x 12mm if i decide to use it. but lots of untempered 5mm glass aswell. this calculator (http://www.theaquatools.com/building-your-aquarium) says if i go no more than 14" high i can like 1 000 000cm X 1 000 000cm or more? just doesnt seem right? but at 16" high i can get almost 4' square? anybody actually used 5mm glass? how high can i go? what are some different dimensions people have done/seen themselves? maybe long and skinny? i just need room for my FW id sharks to swim and if i have to buy a tank its goin salt! help muchly appreciated! thanx

is there a shape (ie: hex,pentagon,rectangle,square...) that might me structurally more stable?

Hex probably with thin glass would be ok. But personally that's pqrette thin glass.

ya i think its thin too. i built my sump with no issues and that calculator says i can go quite large? i searched 5mm glass here on canreef and this guy had a 60 gal over 20 inches high that was professionally built will 5mm glass as far as i could tell?

I wouldn't go bigger than 20G it's too risky. I would be constantly be worried about the pressure, my tank is 18" tall and has glass twice as thick.

You can build alot outta 5mm if you build it correctly.
I build 90g outta 6mm salvage all the time, you just have to brace and cleat it properly

with the 2' x 2' base I'd say 20" tall with a decent euro brace is fine but probably as big as you'd want to go. It's not really the seams you have to worry about or the tank holding together. If the glass is too thin it will bow/budge causing distortion which can be really annoying.

+1
Euro brace and inside brace the bottom and you should be fine. I have seen a 55g fresh water system of 5mm and it was like 5 years old. Just don't cheap out on the silicone as the sandwich joint between your edges will not be very thick. Also I would run your long sides about 3mm past the edges of your short sides so you can create a double joint and seal the inside corner as well as the outside corner.

5mm? Are you sure its not 6mm/1/4"?

thanks guys, i was afraid i wasnt going to get any input here... so that sheet for the base is actually a circle 42" round (not so sure its tempered anymore either? will find out tho if i have to cut it). i figured without even cutting it tho, i could maximize the size by building it hex right on top. would work out to 20" panels be about 3' across, and have just enuf room left in front to rest your elbows while staring at the tank.....

my questions are,
1. would the hex be good idea or bad idea?
2. is 3' across a little to large, should i go smaller (how small)?
3. if hex is a "good idea" and "(whatever size chosen)" how tall then?

a) 20" panels 20" h would be almost 90g
b) 20" panels 16" h would be just over 70g
c) 16" panels 20" h is like 58g
d) 16" panels 16" h would b 46g.

im leaning toward (B) maybe (C), if its a better idea? (A) would be ideal and (D) well..., ill go with the 20" cubeish if thats the case (50 gal)?

thanx