Does anyone have an idea of how much Texas Holey Rock would be suitable for a 55 gallon tank? I am doing an african rift tank with either mbunas or tangs but I was not sure how much I should buy? Does anyone have a ballpark number in terms of pounds? I do not need to absolutely top out my tank in rocks especially since it is a 55 gallon which does not provide a huge footprint width-wise, but I still would like to have it filled out sufficient enough to give it that nice panoramic look, maybe so I could still fit in a nice piece of driftwood or have about a 4-6 inch gap in-between the 2 or 3 rock piles. Any help would be greatly appreciated!