How many lbs of this cement will i need?

[poly-nomial]

http://www.monsterfishkeepers.com/forums/showthread.php?t=93242&highlight=diy+background

I saw this guy making a diy background. His tank was 135gallons and he still had a little left over for his tank. Do you think if they sell like a 5gallon tub that would be enough for a diy background like his for a 75g tank?

thanks

 

[haynchinook334]

Really simple Math.....
75x2=150.... The guy had/has a 135gal using:
1 10lb bucket of Quikrete hydraulic cement - $14.99 (kents building supplies)
1 sheet of 48"x96"x2" Styrofoam- $18.20 (kents building supplies)
4 tubes of GE 100% silicone 2 - $23.04 (Canadian tire)
1 2" paintbrush - $0.99 (Canadian tire)
1 bucket to mix cement - Free, (i cut out the bottom of a 4lt water jug)
1 knife - free (used a kitchen knife,one with a broken tip worked the best,go figure)
1 caulking gun- free ( had one already)

10 lbs for a 135gal and he had some left over....
And he had some left over.......What do you think?

 

[poly-nomial]

Really simple Math.....
75x2=150.... The guy had/has a 135gal using:
1 10lb bucket of Quikrete hydraulic cement - $14.99 (kents building supplies)
1 sheet of 48"x96"x2" Styrofoam- $18.20 (kents building supplies)
4 tubes of GE 100% silicone 2 - $23.04 (Canadian tire)
1 2" paintbrush - $0.99 (Canadian tire)
1 bucket to mix cement - Free, (i cut out the bottom of a 4lt water jug)
1 knife - free (used a kitchen knife,one with a broken tip worked the best,go figure)
1 caulking gun- free ( had one already)

10 lbs for a 135gal and he had some left over....
And he had some left over.......What do you think?

Seems like just having half wouldn't be enough. Any other comments?