Hmm. My hammer and frog spawn never reacted much to the treatment. I always removed as much of the slime as possible before the treatment though. If there was a lot of it in the tank then the break down of it may cause irritation. Maybe? I don’t really know. One thing I learned though about after the treatment. If your skimmer has a drain line on the collection cup you can run the line into a bucket to remove a lot of treatment and left over material via over skimming into a bucket.