This is such a complex topic that it is well beyond the scope of the average hobbyist, including myself for a lot of it.
My focus is generally on chloramine, as it seems to be what most areas in North America have switched to, or are in the process of switching to, and it tends to remain at near full strength while in the system. I believe that Duane once said that when tested after 1 week their sample was still at 100% full strength. The water treatment supervisor here told me in the past that a similar test showed the same, full strength after 2 weeks in a glass jar. Chloramine does not break down nearly as quickly as chlorine. How much and how fast that break down takes place will vary among distribution systems based on numerous factors.
Yes, nitrifying bacteria can be present in distribution systems, how much if any will again vary greatly dependent on numerous factors. Yes, nitrifying bacteria need ammonia to be present in order to thrive, in some distribution systems ammonia will be naturally present, in other systems ammonia will only become present via the decomposition of chloramine. (once the chlorine/ammonia bond has split) This is precisely why one of the most common ways to resolve nitrifying bacteria in a distribution system, is to increase the level of disinfectant. In some cases water utilities will form chloramines as a strategy to remove naturally occurring ammonia in the raw water supply, while others may use breakpoint chlorination.
Chloramine kills nitrifying bacteria. Chlorine kills nitrifying bacteria. Both are oxidizing agents that are not bacteria friendly, and not fish friendly. I think that we can all agree on that. These are not facts based on hobbyist hyperbole, but facts based in hard data supplied by scientists who specialize in this field. Many hobbyists have seen the results first hand, tanks that keep going into a mini cycle, and/or dead fish.
The only real questions left are how much, and how long? This is where disinfectant type, residual levels, and contact time all come into play.
Obviously someone like Dr. Tanner with such a low disinfectant residual doesn't have any issues, he could probably spray the water in while refilling his tanks and not even have an issue if he didn't use a water conditioner. At least in an established tank full of organics, and the volume of incoming water wasn't too great. Many people have stated that they do just that, and have for many years. For those folks, disinfectant becomes a non issue.
But that doesn't mean that someone on a different system, with disinfectant residuals several times higher (at the tap) could safely do the same thing. Again, residual disinfectant levels, contact time while cleaning, as well as how established ones bio-media is, will determine how safe tap water is to use, or not.
This type of discussion reminds me of many others posted here and elsewhere over the years, where hobbyists are asking how much water conditioner they should use (often Prime), and others will chime in stating 1 capful per 50 gallons, as somehow through internet magic they know the OP's water parameters, including their local water treatment plant disinfection levels, or the residual level at the OP's taps. One capful per 50 gallons, as everyone should know, is based on a specific amount of disinfectant residual. It amazes me that many hobbyists still do not understand that basic element in adding tap water to their tanks. Many under-dose, and I think that it's safe to say that many overdose. The reality of overdosing issues, causing 02 depletion, is why Seachem dumbed down their recommended dose 3 years ago.
And finally, there are systems that during part of the year use chloramine, and part of the year use chlorine, sometimes even different sources of water. And there are systems that are currently on chlorine, but are switching over to chloramine.
This topic has never been answered with a one size fits all.
And on that note, impossible to say with any real certainty, Ben. If the tank had enough decor (gravel, wood, skulls lol, etc) and the bio load itself wasn't too high, one might be ok. With a large bio load (fish/food) and a bare tank, the tank will most likely crash. Same result when certain meds are added to a tank, even an established tank. Been there, done that, and in my case it wasn't what I would consider a mini cycle. Some bio bacteria most likely survived the meds, but the majority were clearly wiped out. The problem with nitriying bacteria is at least from my understanding they don't multiply nearly as fast as we would like. Having some back up established media can sometimes be a real blessing.
http://www.bioconlabs.com/nitribactfacts.html
"Nitrifying bacteria reproduce by binary division. Under optimal conditions, Nitrosomonas may double every 7 hours and Nitrobacter every 13 hours. More realistically, they will double every 15-20 hours. This is an extremely long time considering that heterotrophic bacteria can double in as short a time as 20 minutes. In the time that it takes a single Nitrosomonas cell to double in population, a single E. Coli bacterium would have produced a population exceeding 35 trillion cells."
