Treat only the new water you are adding. Simply add 1 capful or 1 teaspoon for each 1200 gallons of water being treated.

No, PondFirst works just as well at making water safe without having the awful sulfur smell. We want our aquatic friends to be happy; we know that fish have olfactory receptors in 2 pits on their snout which are used to find food, spawning grounds, and much more. Your fish will love our water treatment.

You can add it before or after. Both ways will give the same great results as long as there is good water flow throughout your entire pond.  If you do not have adequate water flow, add PondFirst as the clean water is flowing into your pond to allow our treatment to quickly make your water safe.