Fish In/out Cycles

[TwoTankAmin]

The thing about the fish and ammonia issue is that it ignores the other side of the equation. For a tank to cycle there must be mre ammonia present than the bacteria can handle for some time and the same for nitrite. Just because your aquarium test kit fails to detect it, it must be more than 0. And by an amount sufficient to get the bacteria to reproduce. And because one then keeps it as low as possible, the other side of the coin is the lower level exposure will go on for much longer. But I never hear any discusion of extended lower level exposure and its effects. This can potentially do more harm than higher but much shorter exposures.
 
And to say the fish experience harm is also a bit vague. On a day the air pollution is high you may cough , wheeze, get a head ache etc. But once the air clears back up there isn't permanent damage. That pollution can kill you if you live with it day in and day out for the long term. Or more of it short term can also do harm. But when one examines the research into the toxic effects of ammonia and nitrite and even nitrate on fish, the conclusions are not the same as one reads on forums.
 
Read the Merck Veterinary Manual and you will see it says:

Once NH3 is released into the water, it enters the nitrogen cycle, a natural process in which bacterial populations change ammonia to nitrite (NO2) and then to nitrate (NO3). Nitrate can be anaerobically converted to nitrogen gas (N2), which is volatile and quickly leaves the system. Plants or algae in the system may use nitrogen products directly.
 
NH3 is highly toxic and frequently limits fish production in intensive systems. It is also dynamic, and when it enters the aquatic system, an equilibrium is established between NH3 and ammonium (NH4+). Of the two, NH3 is far more toxic to fish, and its formation is favored by high pH (>7) and water temperature. When pH exceeds ~8.5, any NH3 present can be dangerous. In general, a normally functioning aquatic system should contain no measurable NH3 because as soon as it enters the system, it should be removed by aerobic bacteria in the environment. Ammonia test kits do not typically measure NH3 directly but instead measure the combination of NH3 and NH4, referred to as total ammonia nitrogen (TAN). A TAN <1 mg/L is usually not cause for concern unless the pH is > 8.5. However, if the amount of NH3 is increased, an explanation should be sought. The amount of toxic NH3 present can be calculated using the TAN, pH, and water temperature. When NH3 levels exceed 0.05 mg/L, damage to gills becomes apparent; levels of 2.0 mg/L are lethal for many fish. Fish exposed to ammonia may be lethargic and have poor appetites. Acute toxicity may be suggested by neurologic signs such as spinning, disorientation and convulsions.

from http/www.merckmanuals.com/vet/exotic_and_laboratory_animals/fish/environmental_diseases_of_fish.html?qt=&sc=&alt=
 
So they are telling vets that a 1 ppm or lower reading for Total Ammonia-N (which, if tested using an API type kit, would be about 1.3 ppm) is not usually a cause for concern unless the pH is over 8.5. But that would seem to contradict the statement that, at .25 ppm on an API kit, a 50% change is needed during a fish in cycle.
 
IMO, the real problem with fish in cycles is they are much more difficult to manage than fishless. The worst mistake one can make during a fishless cycle can only result in one being back at square one and having to start over. The worst mistake one can make during a fish in cycle can result in a tank full of dead fish that did not die a quick or easy death.