I have a 75 gallon and 150 lbs may be overkill, 150 gave me about a 4 1/2" DSB, if you only want a 2 inch try 100 lbs. You may need more but see where you are with 100 first.
how deep does that make your sand bed peace? crcoachm only wants 2 inches so they're not going to need a whole lot of sand.
could probably get away with getting mostly live sand too if money isn't a problem.
how much sand you need really depends on what type of tank your gonna have (FO, FOWLR, or Reef). people still have FO tanks with bare bottoms(not including the LFS tanks). If your gonna do a reef then you want at least 4" depth.
This should help you out. Just type in your tank dimensions and you will get an idea of how much you will need. It worked pretty acurately for me.
Kyle http://www.purearagonite.com/SandBed.html
well the switch is done
we went with 120 lbs got a good 2 inches
no cloudness we used the plastic tarp method when putting back the water and it work great
plastic started to float after awhile but we kept pouring on the plastic