When buying live rock, most sources suggest using the 1-2 pound per gallon formula, or something else along those lines. While I generally believe that this is too much rock and I’m not a fan of sticking by useless formulas, it’s a good idea to buy more rock than is needed. If you buy just the right amount of rock, in pounds of course, then you have to use each and every piece just to provide enough area for corals to attach to and fish to hide in, regardless of how ugly a particle rock is. If you buy far more than is needed, however, then you have plenty of options. Pick the rocks that fit best together, then get rid of the rest. You can sell the rocks to a fellow hobbyist or use them in another application, such as a refugium.