I was very hesitant to purchase Fritzyme Turbo 700 because of the cost, my concerns about viability during shipping (survival of bacterial colonies), and from reading hundreds of reviews over the years on OTHER bacteria-in-a-bottle products that ended up being total wastes and not effective at all. I'm pleased to report that after introduction of about a 2-3x concentrated dose to my tank (the full 4oz bottle in my 125 gallon) for 2 full weeks now the ammonia has been near 0, and this is a heavily stocked tank WITH 3 species of goldfish and a literally brand new tank and Fluval FX6 filter. I'm impressed not simply with the product, but with Flip's communication after I wrote an email in asking about the delay on shipping. Luckily for me the product didn't need a cold pack to be included since it's fall, and I'm only ~2 hours from their warehouse, so it all worked out.