I was running biopellets on two of my tanks, the 125g reef and the 60g reef. I did not see any real benefits in my 125g after 5 months other than some phosphate levels staying lower. I took it off the 125g for now BUT I have seen some improvements on my 60g tank. I havent seen the nitrates really rise and the phosphates are lower than I started with.
I wouldnt say it is a must have solution to high parameters but it does help from my experience.
Here is a link from bulk reef supply that explains how to use them which i found helpful
BRS Biopellet Instructions - Instructions - Bulk Reef Supply