Quoted from the link above under the cycling section.
Beneficial bacteria thrive best at a pH of 7.4 to 7.8 and in water with lots of carbon dioxide. So, adding one teaspoon of baking soda per 25 gallons speeds up the cycling a little bit.
Lots of aeration will both speed up the cycling process and keep the smells down (cycling can be smelly!).
The optimum level of nutrients for beneficial bacteria growth is 400 to 600 ppm of ammonia and 200 to 400 ppm of nitrite (per no less than 8 papers and two books). So high levels of either ammonia or nitrite do not stall the cycle.
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Beneficial filter bacteria are aerobic and require oxygen rich water. Having lots of carbon dioxide (CO2) in the tank will inhibit the filter bacteria. The next sentence contradicts the first paragraph by saying aeration helps speed up the cycling process. This is true, aeration helps to drive CO2 out of the water and helps keeps the oxygen levels high. This can help the filter cycle faster.
re: Having 400-600ppm of ammonia in the tank while it was cycling. That much ammonia would burn your nose and eyes any time you went near the tank.
Sorry, I couldn't read any more. Just too hard to read anything these days (that includes stuff online or in books).