How much live sand for a 5.5 gallon tank? long story i was walking into my local fish supply store and i saw they were getting rid of all the salt water supplies. they had no live rock left so i had no choice but to get a 20 pound bag of live sand and one pound of dead and dry reef rock. i already have 3 ish pounds of live rock but no sand. how much sand should i use? pounds and inches of depth plz.