NOPOX is incredibly easy and effective. Like magic for reducing NO3 and PO4. Much more effective and straightforward than biopellets in my experience. I haven't had any negative side effects that I can see. The directions are dramatically easier to follow than the other various carbon dosing regimens I've seen out there, presumably due of a better safety profile or just more research. The only problem is that it may reduce your levels too much so you have to test often until it is dialed in.