Dump the bio balls if you have more than 100 lbs of live rock and sand. I heard to do it slowly, but I recently removed all bio balls at once and my nitrates (which constantly sat at 20) dropped to 5 and I havent noticed any negative effects of removing the bio balls. Look into the Berlin method of filtration. I am now a believer that any type of filter media and live rock kind of counteract eachother and become nitrate breeding grounds. Make sure you are running carbon.