I was thinking the same thing. We have no way of knowing for sure that the product is working.
The only way is by observing the fish. If the fish act strange then the product might not be working.
If the don't die then it might be.
What I did was change about all the water when I knew the filter was working. Then tested for
ammonia and
nitrite. That way I know most of the Prime is out of the system and I can once again trust my water testing results.
