William_

Thank you very much @Hobbit!

And on another topic; Is there any books or website dedicated to the aquatic nitrogen cycle? I've read books on the nitrogen cycle for Agricultural science but nothing purely on the aquatic nitrogen cycle itself and how it relates to the health of both the fish and plants in my aquariums.

I test my tanks constantly. They're on a rotational schedule so I always know the levels. The ammonia and nitrite are almost always 0ppm but the nitrate holds a steady 10-20ppm range which I remove with water changes of course. I don't have a lot of plants, mostly moss, so the nitrates don't really have a place to go. Are the Nitrosomonas and Nitrobacter really that efficient in converting ammonia into nitrite and then into nitrate respectively, or perhaps I don't have such a large load that the levels would fluctuate as I've seen in examples by other people?

Thank you for the info guys. My worry is removing the water too much will also remove the food source for the Nitrosomonas and Nitrobacter Bacteriums. Causing a massive die-out in the filter and on the substrate spiking the ammonia and killing all my fish before the Nitrosomonas bacterium can come back to reassert the cycle. Any thoughts?

My wife and I have recently dove head first into this hobby and we love it. I am a bit confused about the water changes on a cycled tank. We have a 29 gallon that has been running about 2 weeks. I tested the levels along the way and when I saw the ammonia make its way into being nitrates at a concentration of 40ppm I did a 50% water change. tested again and they were just under 20ppm maybe around 10ppm. After a few days I did another water change and the levels were around 5-10ppm (I have the API freshwater master test kit). My question is : We got some guppies to put in the tank and of course then came fry. Just before this happened we had a huge nitrite spike of 5ppm. I did the necessary water changes to get that back to normal and everything has been fine since. The real question, is doing to many water changes going to hurt the fish? Even if both types of bacteria are present and doing their job, will removing and replacing to much water hurt the cycle and is it dangerous for the fish, especially the fry?