At about day 10 into the cycle, the nitrifying bacteria that convert ammonia into nitrite, nitrosomonas, should begin to appear and build. Just like ammonia, nitrite can be toxic and harmful to marine animals even at lower levels, and without nitrite present the cycling process cannot complete itself. Nitrite will continue to rise to a high level of about 15 ppm, the most critical stage, and at about day 25 the level should begin to fall off, although it's quite possible to run on for another 10 days. Most likely the nitrite reading will peak and fall off to less than 2 or 3 ppm by about day 30, and shortly thereafter to zero. If it does not, don't worry, it should drop sometime within the next 10 days or so.
Phase 3 - Nitrate (NO³)
Now that the ammonia has given birth to nitrite, the nitrite in turn give birth to the third and final nitrifying bacteria, nitrobacters. These bacteria are living entities that require oxygen and food (an ammonia source) to survive, grow on the surfaces of everything in the tank, and the waste from nitrobacter are shown in the form of nitrate with a test kit. When nitrate readings begin to increase, you can tell that these beneficial nitrifying bacteria are starting to establish themselves, which is what you have painstakingly been going through the cycling process to achieve.
So once your tank has reached the end stage of this process, what do you do next?
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