how much sand do I need?!?

[pckroeger]

I have a 100L/26g tank, dimensions: 66cmX39cmX48cm/26inX16inX19in (LXWXH).
How much sand do i need to adequately cover the tank bottom??

[Cermet]

That depends on your objectives - if to just cover the bottom, very little, maybe an inch at most. For plants, at least two inches and somewhat deeper in the back to give a slope effect; and to create a bio-processing very low oxygen nitrate absorber, three to four inches deep. These values all assume sand; gravel would be at least 50% greater for each case.

If you just mean bag weight to achieve some arbritary but useful depth, well, for a 26 gal tank, I'd guess between sixteen to twenty-five pounds.

[Cliff]

+1 to the above

I have about 1.5 inches in my tank with a moderate amount of plants which seam to work very well. If you don't want/plan on any plants, then I would suggest 3/4 to 1 inch to make routine maintenance a little easier

[korith]

Try this calculator
http://www.plantedtank.net/substratecalculator.html

I agree with the others, you don't want the sand bed to be too thick.