actually the prime is cheaper, the bottle might cost a dollar or 2 more but will last through many bottles of the aqua safe, aqua safe treats 20 gallons with 10ml, prime treats 100gallons with the same dose, actually a whole lot cheaper than aqua safe, use whatever you have, but the next time you buy, consider the prime, and if you drain and clean the whole tank, you'll probably be hit with a big cycle and not just a mini cycle.