The product Cycle is supposed to contain the bacteria that create the nitrogen cycle.
The concept is that you are simply adding the bacteria you want instead of waiting and letting them self propagate.
I have used it several times in my QT
, because I feel that it is extremely important to lessen the stress of ammonia on fish when they are new or sick. This is usually difficult to do when there is no bio filtration at all in that tank. I was very happy with how it worked and used it when I started my 75gal SW
. Nitrate was present the next day with minimal ammonia after 2 days. I added a damsel in three days! I waited two weeks to add more fish because I was nervous, but the measurements never spiked.
I think that there are several factors to the use of this product, including the age of the product and how the bacteria are preserved, but my experience has only been positive. I will continue to use it to "prime" the filter in my QT
and I would use it if I were to start another tank.