With tetra safestart I have used it on two of my tanks. On my first tank I followed the directions that I had found online from a Q and A that was done on another forum with tetra. In this they said to not do any water changes for two weeks. At the end of the two weeks, my ammonia, nitrites and nitrates were all high. I ended up carrying out some major water changes over the next few days to get the levels where they needed to be. The second time I used tetra safestart I did water changes on the tank when ever ammonia or nitrites called for one. In a couple of days of adding tetra safestart I was getting readings of nitrates in this tank. At the end of the two weeks I had a nitrite reading which with a water change it took care of that, and my tank was cycled. I would suggest that even with the tetra safestart to keep an eye on your water parameters and keep up with water changes as needed. The bacteria in the bottle will help your tank in establishing the bacteria that it needs in the tank, but levels can still get too high. If you want on my 50 gallon and my 20 gallon convict tank, are the tanks that I used tetra safestart on. I kept track of my testing and my water changes that I dd in the parameter and maintenence section. Doing the water changes in my opinion did not make the product less effective, and I felt that my fish were kept in a healthier environment by doing the water changes.