i started with 100lbs, now i'm at about 140. if you can't overstock a tank with fish, buy lr or equipment. i've seen plenty of tanks that have much much less, but i personally wouldn't do less than 45lbs in a 55. that kinda looks tacky and empty to me though. different lr is different densities however, so a really porous rock will appear a lot bigger and hold a lot more beneficial bacterias. the base rock i've seen is pretty dense and heavy as heck, so poundage is relative.