Just took a trip to the pet store. Help please!

[Olympia]

Most likely your tap has chloramines. Prime will detoxify the chloramines but will leave ammonia behind, only way around this is cycling the tanks..

[aokashi]

prime also detoxes ammonia. not sure how that works, probably binds both the chlorine and ammonia when it detoxifies chloramine.

[Olympia]

Ammonia is only detox'd for 24-48 hours before it re-binds. The product turns it into ammonium, in basic water it will become ammonia again after a time depending on how high the pH is. In acidic waters ammonia present as ammonium constantly. Ammonium is considered much less toxic to fish. Our tests test for both ammonia and ammonium, so the readings won't change even after Prime is used.
It's good if you're too tired to do a water change one night, or fish in cycling (dosed daily), but not a permanent solution.

[aokashi]

yup, I kinda meant, it'll cut down the toxicity right out from the tap. XD