40 lbs of sand will give you a 3/4 to 1 inch sand bed you can mix pool sand for deeper bed if you want. you can seed base rock (and your sand) with a cup of live sand from your LFS
some will give you a cup free, some may charge up to $5 for the same cup. or you can use as little as 1 lb of live rock. That's what i did i bought 100 lbs of base for a 90 gal
. and one 1.5 pound piece of LR
. to seed it.
Most people create their own problems by not following the basics and refusing to stock appropriate to their system. Gregcoyote 2013
SPS = Stability Promotes Success