I used it when I suspected I had AEFW, and what I noticed is increased slime coating during conditions where corals slime, taking out of water, basting, after feeding, the normal conditions that induce sliming. This increase in sliming is what the corals use to protect themselves from AEFW, the worms do not like the slime. So, does it kill AEFW, no, what it does is increase the health, in turn the sliming effect. Combining certain wrasse, blue leg hermits, peppermint shrimp, and dosing the KZ Flatworm Stop, and I could not find them on any corals within 6 months. I feel the product works