i have q 20 gal long and got 25lbs of med size natural pea gravel, cic addict its right, i wish i went a lil smaller in size of gravel but i would always go at least 5lbs more than the 1lb rule per gallon..25 lbs for a 20 gal long is just about percect it gave me almost 3-3.5 " of coverage nessesary to bury the anchor trays for most artifical plants..i even was able to slope it a little back higher to the back actualy coulda used another 5lbs...my next tank il be doing will be a 30 gal long and plan on geting 40lbs, so i can set up one terrace...but i would recommend 5 lbs more after the calculated 1lb per gal rule, you wont be sorry, trust me...it gets spread out fast!!!!! i rinse mine too in a pasta strainer till water runs clear, then just take it over to empty tank and dump it all in then begin to landscape it.....works for me!!!! lol good luck, your gonna get addicted FOR SURE!!!!!!!!!!!!!!!