yeah FWE is a mixed blessing for me. I dosed it once, and had so many I didn't see (that I didn't syphon out) and my water did turn visible red from the toxins they released (and yes I was trying to scoop them out as soon as I saw them) all fish survived that night, but the next day my foxface that ate anything vegetable (most notable algae I didn't like) was floating, a couple days later I didn't see my bicolor angel in the tank anymore, assume he died in the rocks.
Worst of all, I didn't get them all, and they're back with a vengeance, so I try to live with them, I try to siphon them, I was tempted to use FWE again, however I couldn't find the bottle. So $22 bottle of the stuff which cheesed me off is "missing" vs potentially killing more of my fish... mixed blessing.