Phosban reactors can be worth it if you have a problem with PO4, if not then they are worthless. It maybe best to run a small one to help with the PO4 that is added with food and stuff. You are correct also CA Reactors are worth it to anyone with a large tank and many clams/SPS Corals. Many people have also used a Phosban reactor to run carbon, this is also a good thing