i am recovering from treating with FWE, what i thought was 2-3 dozen worms turned out to be hundreds. i was not prepared for so many, even after doing 25% water change on initial treatment, my water still had a reddish/orange haze from the die-off of flatworms. i lost a few nice sps frags as they do not tolerate the toxins well. do not under estimate the damage they can do.