If you only have 1 or 2 pounds, I'd say you certainly need more. Of the less dense live rock, I like to see at least .5 lbs per US gallon, more with dense rock. Of course, once you reach a certain amount, it is a matter of taste as to how much more/less you want to add/subtract. For people just starting out, 1 lb per US gallon is a good rule and the added rock can help make the tank more forgiving in terms of certain chemical parameters. Later on, you can certainly experiment with more or less. For example, in my 75, I probably have around 45-50 lbs of live rock to get a unique aquascape and maximize flat surface area for corals.