IMHO, there is no need for it. If you do not bring anything into to the tank, it won't appear. I don't know the products specifically, but I am not big on using anything that is not necessary, in general, I don't use anything, just water changes, life phyto, and sometimes purple up. In my opinion, garlic is snake oil, others swear by it. Corals are so sensative to every chemical in water since they are filter feeders, I can't see how in the long run, this will not at least annoy them. I guess Metronidazole is an anti-biotic, so, after awhile, it will not work. Besides, anti-biotics need to be used regularly and for a short period of time.