I would suggest catching a fish first, any should do... but preferably one with symptoms. And performing a 5-minute freshwater dip:
If you confirm flukes, there is relatively low risk involved with treating a reef with some caveats:
Biggest risk is oxygen depletion, so you'll want to be sure you have sufficient water movement and surface agitation. Also, its advised to keep your skimmer running, just remove the cup so it overflows back into the tank.
It may harm ornamental worms/feather dusters. It shouldn't harm corals or other inverts. Most fish tolerate it just fine, but wrasses can be sensitive to overdose.
Some anecdotal experience: I didn't notice anything out of the ordinary during the normal two doses, but had to dose a third time due to circumstances. After the third dose, I did notice some reduced PE and sliming of corals, but had no casualties or real damage. I've never tried dosing with an anemone, but I have heard some say their nem looked "unhappy" after treatment, but haven't heard of any casualties personally.
