Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Prime is primarily a dechlorinator. It breaks apart the chloramine bond and locks up the chlorine and ammonia so they are not toxic to the fish. Nitrifying bacteria can still access the ammonia, and in a cycled tank they remove the ammonia. I do not know what happens to the chlorine.
Prime also locks up nitrite and nitrate. I think nitrifying bacteria can still get to the nitrite.
I am not sure what happens to the nitrate. Perhaps live plants could use it? Perhaps the anaerobic denitrifying organisms can use it? Maybe the only way to get rid of it is with water changes.
Best use as a dechlor is to mix it with the new water at the dose stated, then circulate that water a bit. Action is very fast, so you can pretty much immediately put that water in the tank. (I would add the dose to a 5 gallon bucket, swirl it once with my hand, then dump it in the tank)
As so well illustrated by plantedrich, you can also dose Prime as you are refilling the tank, but dose for the whole tank volume.
Best use in emergency (high ammonia or nitrite) situations is to do as large a water change as possible, then dose Prime per label directions for the amount of ammonia remaining in the water. Adding sodium chloride for nitrite toxicity can be done at the rate of 1 teaspoon per 20 gallons.
In case of ammonia or nitrite emergency try to do enough water changes, frequency and volume, to keep the ammonia under .25 ppm and the nitrite under 1 ppm, then use salt and Prime to help out. (of course solving the problem of where these toxins are coming from is part of the solution)
As for the other claims, I am not sure my fish need an enhanced slime coat; they are producing all the slime coat they need.