As I've written in another thread, I've been using Hydroton in several large media reactors to greatly reduce my nutrients. I've never had low nitrates due to my habit of heavily feeding my fish (4-6 times daily) but now, with media reactors full of Hydroton, my nitrates are very low, (around 2 ppm last time it was tested with a Hanna tester by Monocus) and my corals have been extremely happy. I have had several other local reefers try out hydroton with very good results. My nitrate tests always used to show in the Fuscia range

but now even my new SPS corals are colouring up within days of being added to my tank, which is a mixed blessing cause now I'm starting to collect a few more SPS
However, this new use of these clay balls developed for Aquaponics was originally tested and proven by Paul, from Oceanic Corals, who convinced me and a few other local reefers to give it a try. To be honest, a gallon or two of Hydroton is more effective at eliminating nitrogenous wastes than a hundred pounds of live rock. I leave my live rock in my tank so my corals have a place to grow and my fish have places to swim/hide. I depend on the hydroton to do my biological filtration.
Anthony