I have 150plus... in my 75gl...... 50lbs of fiji, and I made about 80lbs of argocrete rocks that is all becoming live as we write... I dont personally think there's a rule for the live rock. U can put as many lbs as u desirre. Do it how u feel. Or think of how the fish would like it or the envoirment it actually came from. "Like if u want mandarins u need a lot of live rock" Build the tank for the situation. My other 90gl has eels and puffer and I don have a lot of rocks!