With the flat worm exit, I suggest following the directions as far as getting rid of as many of the worms as you can before treatment.
Flat worms release toxins when they die, while a few couldn't kill much of anything, you are looking at hundreds id not thousands, estimate what you see and multiply by atleast three.
Once you feel like you have gotten what you can with a siphon, I double what the package says for dosage, because I can treat my tank several times with one bottle.
Wait for a few hours, or until you see corals getting really irritated, then do a 25% water change and add a good amount of carbon.
next day I suggest replacing the carbon, but for that first 24 hours you will want to keep checking on your corals as much as possible to make sure they are ok.
Two weeks later if you don't see any worms, double dose again to be sure.
Flat worm exit is not dangerous to corals, or fish, or anything else in your reef as far as anyone has found so far. But the toxins in the water from the flat worms dieing can be very bad if there are enough.
i have treated probablly 4 tanks in the last year with flat worm exit and I have not seen one fish die, and we have lost very few corals, most likely those were lost due to stress on the system due to some major water changes.
One of these tanks were my own, and it has been a couple months with no sign of flatworms, and I have not lost one coral or fish due to the treatment.
