Just by way of an FYI. When it comes to nitrifying bacteria in nature, there are all kinds and they are not all equal. This is especially true for the ammonia oxidizers. While pretty much most of the different ones are present. even if to a small degree, in most waste water treatment plants. These are the high ammonia environments where ammonia levels will also fluctuate greatly.
But in tanks, which is a very low level environment, the bacteria that do best at such levels are mostly what are found. However, when it comes to the nitrite oxidizers, there seems to be much less variety. The Nitrospira dominate in many environments, especially when nitrite is at the levels typical in tanks. And this is where the problem with finding a good bottled product becomes a factor.
When the group of researchers discovered it was nitrospira in tanks and not the Nitrobacter winogradsky as previously thought, the game changed. They were able to obtain a patent on them as well as the method for detecting them. This is one reason many bottle bacteria products do not identify what is in them. Those that do usually will say they contain nitrobacter.
But there is another big clue I look for in all these products and if you think about it a minute it makes perfect sense. When one cycles a tank using media from another cycled tank, how many time do you add media? Once (unless you only had a little and you find some more). So why do some bacterial starter products say to add it every day for a week or several times in the first week? If it is the proper bacteria and in good condition, why should it require more than a single addition? Of course the makers all have ideas about when else one might use the product, such as when adding new fish or after medicating, which may make a bit of sense sometimes. But in an established tank, why would one ever need to add bacteria regularly? On reason I use Dr. Tim's ( and there area several) is the followihng from his site on how to cycle a tank using his bacteria:
Using DrTim’s Aquatics One & Only Live Bacteria: The best and easiest way to fishless cycle is to combine adding the ammonium chloride with our Live Nitrifying bacteria. When used in combination, these will cycle the tank in less than one week. Again, do not add too much ammonia. We make it easy by providing a bottle of reagent grade ammonium chloride that is at a concentration such that adding 1 drop of solution to 1 gallon of aquarium water will result in an ammonia-nitrogen concentration of 2 mg/L (ppm).
The procedure is to add the ammonium chloride solution, shake the bottle of nitrifying bacteria well and add it to the aquarium. Measure ammonia and nitrite the next day and record. Add ½ dose and wait 24 hours and measure again. By day 5 to 7, you should be able to add 1 drop per gallon and the next day, ammonia and nitrite will be 0.
from
http
/www.drtimsaquatics.com/resources/how-to-start
For my part I normally do not need bottled bacteria because I have enough running tanks to set up a new one and instantly cycle it. However, There are situations where I do need it. Most notably where I need to cycle a new tank without taking anything from an established tank because the fish going into the new tank have little or no resistance to most of the domestic nasties living in our tanks Because the incoming fish do not have any resistance, they need to be in a more "sterile" tank at the outset. Bottled bacteria is the ideal cycle starter in such cases.