I just picked up a bottle of Prime and want to use it with today's water change. I will be doing a 50% pwc and am not sure how much to use. I've got a 10 gallon tank (so will be changing 5 gallons). The new water is sitting in gallon milk jugs. Any idea how many drops to put in each jug? The directions say Prime can be added directly to tank water, so I suppose I could just add it after putting in all the new water, but my fish are already very stressed due to high ammonia/nitrite levels so I want to make this easy on them. Also, the directions say that in extreme conditions you can use up to 5x the amount of a normal dose. Is this really safe? As said, I don't want to stress these poor fish any more than they already are.