My zeovit tank has been running 2.5 years. Zeovit is very effective to maintain very low nutrient level. I never have the issue for the nutrient such as PO4 and NO3. However, I lost a couple of SPS colony with other reasons like low salinity and high KH, but it is nothing related to Zeovit system.
It costs little bit more than other system. All-In-One biopellet might be better than Zeovit, but I am afraid to change the system.