Ammonia Toxicity And Fish- What The Research Tells Us

[TwoTankAmin]

I know I am a lone voice on this, but I still see little reason to abandon my stance on what levels of ammonia or nitrite are harmful to fish. This is usually only an issue during a fish in cycling for most of us as we may not see an ammonia reading in a tank ever once the tank is established. For the purposes of this discussion I would like to limit the topic to ammonia only.
 
My argument had always been and still is with the concept that during fish in cycling, any reading of ammonia is intolerable and water changes must be done. I have said this many times before and will say it again. that statement about ammonia is simply not factually correct. I would like to offer more on this as food for thought.
 
The most important fact to understand is that different fish have different levels of ammonia they can handle. There is no universal number for this.
 

 
Length of Exposure
The concentrations of ammonia that cause toxicity to fish depend on the length of exposure.
Lower concentrations may not kill or adversely affect fish over short periods of time, but the
same concentrations could kill or impair aquatic life under longer time frames. US EPA
recommends an acute ammonia criterion of 2.9 or 5.0 mg N/L (for short-term exposure) and a
chronic criterion of 0.26 or 1.8 mg N/L (for long-term exposure). Water with concentrations of
less than 0.020 mg/L unionized ammonia is considered safe for fish reproduction (EPA 1989).
As shown in Figure 3, lower and lower concentrations of ammonia are tolerated with increasing
pH values under acute (short-term) exposure scenarios. The same is true under longer term
exposures (Figure 4), and lower concentrations are tolerated under higher temperatures.
A single or simple concentration measurement of ammonia is not sufficient to evaluate and/or
regulate ammonia contamination. The influence on the toxicity of ammonia to fish is impacted
by both duration and frequency of exposure. Duration of exposure to ammonia has been
demonstrated to be a critical factor affecting fish survival - and should therefore be incorporated
into chronic and acute standards.

from http/www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=19&cad=rja&ved=0CF0QFjAIOAo&url=http%3A%2F%2Fwww.nature.org%2Fcs%2Fgroups%2Fwebcontent%2F%40web%2F%40alaska%2Fdocuments%2Fdocument%2Fprd_026308.pdf&ei=1Y7MUd64ENj64AOa-oDACQ&usg=AFQjCNExALy9-xsoUKsVESpMs0bRDU-WRQ&bvm=bv.48572450,d.dmg
 
What I keep seeing is that not allowing some accumulation of ammonia and nitrite as it shows on the API kits is not the wrong thing to do in most instances. This information combined with the selection of cycling fish that are more resistant to the effects of ammonia sure seems to indicate to me I am on the right track here.
 
A few more interesting factoids I have also picked up:
 
The odds are good that exposing fish to ammonia that may be harmful and then removing that ammonia so the fish can recover but then having this followed by another jolt of ammonia causes that second jolt to be even more damaging.
 
We know that it is NH3 which is the toxic form of ammonia because it can pass though the gills into the fish's bloodstream but NH4+, the way less toxic form cannot. What I learned was that, once inside a fish, NH3 gets converted to NH4+ and it is this form that actually causes the damage inside the fish.
 
There is also evidence that fish which have been recently fed have a greater resistance to the effects of ammonia than fish which have been starved. This of course would fly in the face of the advice when ammonia shows up in a tank to feed sparingly. I am going to have to look into this further.
 
 
 
 

 

[stanleo]

This makes sense but is very complicated. When giving advise to new fishkeepers is it not best to give the simple answer. Ammonia is toxic to fish, so you need to do a water change at the least to alleviate the problem.
 
I do however agree that a fish-in cycle is not the wrong thing to do as long as it is done with fish that can tolerate an increase in ammonia.

 

[levahe]

I agree, for the 'noob' fish keeper the best solution is to keep it simple and have easy to follow instructions for everyone (fishless add ammonia cycle)

This is something for the more advanced aquarist to get their teeth into.

If I had it my way people would all start with a planted tank doing a fish in cycle with a very low bioload and just let the cycle complete naturally. There is no way I would ever dump ammonia into an aquarium!

 

[TwoTankAmin]

I agree that fishless is the way to go. The problem is not 100% do it that way. So what do we tell people who want to do a fish in and cannot be dissuaded or have read about one and tried it? Would it not be better to to have an article on a site which suggested in big red letters that folks should always go fishless if at all possible and then say, if you can't or won't or are already started read this: and then explain how to do it properly?
 
I still believe that having people shoot for numbers under .25 ppm for ammonia (and more so nitrite) are likely doing more harm than good during a fish in cycle. I have brought up this topic before and I keep coming back to it as I read more and more.
 
There really is a great deal of difference between cycling a tank and running a fish farm. A lot of the research on toxicity relates either to situations in the wild or in aquaculture. We as hobbyists have to work to figure out those parts that are applicable in our tanks. For example, trout are often used in research. They are a sensitive species and not a fish we are ever likely to keep in our tanks. So what level of ammonia or nitrite these fish can tolerate is not very relevant to us. On the other hand, studies which look at ornamental fish are much more relevant. A study on cardinal tetras and shipping or on danios and nitrite are much more appropriate since these are fish we actually keep and for which the information become more relevant as a result.
 
There is also a big difference in terms of ammonia etc. in a tank being cycled with fish and that very same tank six months later when it is established and fully stocked. In one the ammonia has to happen and in the other is should never happen.
 
While it is nice to keep it simple for new fish keepers, what if that simple is not correct. What if the research indicating bouncing ammonia levels up and down is more harmful than not doing that? What does that do to the situation where a person is told to do the big water change and the subsequent result is a return to ammonia readings? Then they get told to get them down again only to have them bounce up again?

 

[stanleo]

I agree that fishless is the way to go. The problem is not 100% do it that way. So what do we tell people who want to do a fish in and cannot be dissuaded or have read about one and tried it? Would it not be better to to have an article on a site which suggested in big red letters that folks should always go fishless if at all possible and then say, if you can't or won't or are already started read this: and then explain how to do it properly?
 

I agree 100%! There should be an instruction guide on how to do a fish in cycle. 9 times it 10 I bet new fishkeepers do it this way. (I being one of them!)

 

[snazy]

Well, it's technically not possible to have 0 ammonia/nitrite in a fish in cycle in most cases. The ammonia accumulates in a matter of hours. With daily water changes, even large ones, there still will be enough ammonia/nitrite to affect the fish negatively but cycle the tank, unless one does several daily large water changes.
I used to do fish in cycles in the past and I could barely keep lower ammonia/nitrite levels. It was impossible to keep them even below 0.25, but then again I was sensless with the starting stock too.
I just think fishless cycle is the way to go, or otherwise a heavily planted tank for the more experienced. People just aren't patient enough these days. The available data speaks for itself, most people kill fish in a fish in cycle.
 
As for the food, I always believed it helps with the immune system and better feed and do large water changes, than create an additional stressor and starve the fish.  It's been repeated over and over again not to overfeed fish, but no one seems to realize that starving fish is as bad as overfed fish. I am not sure about the benefits when fish are exposed to ammonia, but if you are stranded on the north pole, would you prefer to be starved and freezing or full and freezing ?
I was once reading an article about transporting otocinclus and it suggested that the best survival rates are when you drop some cucumber inside the bag for them to feed on while there. It's not because they'd starve without it, but because it reduces stress from the additional factors like ammonia and the movement itself.

 

[TwoTankAmin]

Again- I do not debate to idea of going fishless. But even .25 ppm may not be an issue and higher as well. There are myriad factors to consider. The accumulation part is controlled as much by stocking selection at the outset as anything else.
 
The real trick in fishless is to get people to seed the tank. Get some bacteria in there fast if you have not yet. Wait, can you do that? Well of course you can. And here is something neat about that. If you put one or two zebra danios into a tank that is say 30 gals (113L) to cycle it and you seed it with the same amount of bacteria a new fish keeper might be able to borrow if doing a fishless cycle, what happens in duplicate tanks?
 
Well the fish in tank makes its ammonia a little at a time and fairly steadily while the fishless tank gets a 3 ppm dose all at once. You might just never see an ammonia reading at all in the fish in tank while you watch the 3 ppm in the fishless tank take a number of days to get near 0 . You would only see minimal nitrite, and only for a short time, as well in the fish in tank. Nitrite will get higher in the fishless. And neither minimal total ammonia nor minimal nitrite (.25-.50 ppm) for a few day period will harm zebra danios. They may have some brief discomfort, but no lasting effects.
 
In the end if you do both tanks properly there will not have been any harm to fish. The difference will be one tank starts with fish to enjoy and the other ends with a well stocked tank a whole lot sooner.
 
When it comes to fish in cycling, often ITS ALL ABOUT THE SEEDING    

 

 
The challenge is how to get the bacteria to the people who need it the most.

 

[TwoTankAmin]

I just can't help myself. I keep looking for more research for specific reasons and keep uncovering interesting information. I was looking for information on Betta splendens and ammonia toxicity. i stumbled across a study that was intended to research the use of clove oil and eugenol (the principal ingredient in clove oil) as a sedative in the bag water of shipped betta splendens. The tests were designed to investigate this for a 48 hour period.
 
The basic premise behind the study was that stress and activity cause ammonia production by fish to increase. therefore if one can sedate a fish some during transport this should decrease activity and breathing rate which could be evidence by a lower level of ammonia in the bags. They tested this using control fish and then fish at several different concentrations of both clove oil and the eugenol.
 
They produced the numbers for all this which of course produces information pertinent to the discussion of ammonia toxicity and fish. Sorry for the quality- but check out the levels for total and unionized ammonia after 48 hours:


 
Read the whole study here http/grad.cs.buu.ac.th/~52920430/Thesis/Datawarehouse/Interrest/O11_04_AntianxietyActivityCloveOil_Panuwat.pdf
 
I saw no mention of dead fish anywhere.
 
But again I wonder when I see fish in 1.37 to 2.07 ppm TAN but sub toxic levels of NH3 over a 48 hour experiment and then I see a post saying if your TAN is .25 ppm you must immediately change 50% or more of the water or risk bad harm or death to the fish how the fish in the lab lived? or maybe i am wondering where the person who states .25 or .50 ppm of ammonia as read on an API kit is doing big damage or creating a fatal condition when if it is present for a number of days or even a two weeks.
 
As a reminder, some say the level at which NH3 starts harming fish is .03 ppm, other's, including the Merck Veterinary Manual suggest its .05 ppm.
 
But there should be a second takeaway form this research. Stressed fish make more ammonia, fish that bolt make more ammonia. This is why the sedative use lowered ammonia levels in the bags- calmer fish = less ammonia. Where this is relevant is the fact that big water changes do stress fish- you see them bolt and hide. And this is another reason to question the wisdom of doing these over and over to lower ammonia levels that likely don;t need to be. How much ammonia are these water changes creating from elevated stress vs what they are removing?

 

[eaglesaquarium]

I do enjoy reading these posts!
 
 

There is also evidence that fish which have been recently fed have a greater resistance to the effects of ammonia than fish which have been starved. This of course would fly in the face of the advice when ammonia shows up in a tank to feed sparingly. I am going to have to look into this further.

 
This is worth looking into more... but at the same time, many of the people being advised to 'feed sparingly' are newbies and newbies, in general not in all cases, have a tendency to overfeed.  So, the advice 'feed sparingly' may end up bringing the newbie back to a 'proper' level of food.  Excess food will create ammonia all on its own, even if its not eaten.
 
 

Again- I do not debate to idea of going fishless. But even .25 ppm may not be an issue and higher as well. There are myriad factors to consider. The accumulation part is controlled as much by stocking selection at the outset as anything else.

 
I think one of the biggest issues with the fish-in cycles we see on the forums are doomed from the start, because of this very factor.  Lots of people buy whatever fish they think look nice for the cycle, because they don't know any better.  They also buy far too many fish than they should to start, because the tank looks "empty".

 

[snazy]

Even from anecdotal experience one can see fish don't kick the bell once they endure ammonia for a day or two or more, depending on the level and if it's not extremely high. The problem is that the stress from being exposed to ammonia weakens their immune system and they end up sick from all type of diseases. As for water changes stressing fish, that really depends. I do 50% water changes and most of my fish gather around the waterfall and start buzzing around as they think hands in the tank means food too. They definately don't hide.

 

[TwoTankAmin]

snazy- you are comparing fish that have lived in your tanks for some time. You are not doing daily big water changes, you are doing weeklies I bet. Your fish have become used to water changes and are less upset by them. On the other hand fish going into a new tank from a fish store arrive not in the best shape. Then they go into a strange environment which is not relaxing either. I highly doubt if your fish today behave during a water change the same way they did when you performed their first few.
 
And as for the ammonia issue. If you want to tell me that two sets of fish, exposed to identical conditions with one difference, Fish A live in .5 ppm for 10 days and Fish B live in 1/2 that for 4 weeks and that Fish A are more harmed than fish B, I need some form of evidence. I can see studies which indicate to me that Fish A will not be harmed at all, I can also see studies that show Fish B will be. I can find lots of info on stress and the reduction of resistance. I can also find evidence that fish which survive ammonia exposure more than once do better the second time than the first. But this brings me back to the implication, sans evidence, that the stress caused by ammonia exposure at a lower level but for a longer time creates less stress related risk. I am not convinced of this at all.
 
This issue is not quite so simple as being one number and including all fish. For me the answer came from working backwards. I started with the statements about water changes and .25 ppm of total ammonia- not just NH3- and tried to find "proof" it was true. What I found was it wasn't. I did not find that it was never an issue, I did find it really does depend. I also found studies of exposure and full recovery indicating that even in those cases of short term damage, after removal of the ammonia, the fish recovered full health at much higher exposure levels.
 
Few things are ever all black and white. There is a level of ammonia exposure at which fish of any kind can not survive. But below that number its gets pretty variable.
 
What the preponderance of the evidence I have read to date on this has led me to conclude are the exact things I have been saying. I firmly believe that I can do a fish in cycling and have the fish involved all be fine in the end. I know how to select the fish and to stock. I know when to change water and when to let it be. I know how to test. So when I say I have cycled some 75 tanks over the years and only one was done with fish in, there is a reason. There is a big difference between knowing how to do something right and actually doing it. One doesn't guarantee the other. But this doesn't negate the fact that it is possible.
 
But I think perhaps a more important question to ask is, knowing the options at the outset, why would anybody choose fish in over fishless? What reason can anybody give to choose fish in? Even a lack of proper ammonia is no excuse. The only one I can come up with is having fish thrust upon us out of the blue so there is simply no other choice.
 
But in today's world of working bottled bacteria, numerous fish keepers who may share some media and chemical helps such as dechlors that also handle nitrite and nitrate, massive water change are the least attractive option to solve fish in cycling problems. They are, at best, a stopgap to get the fish load down or the above things in.
 
And lets not forget there is a newbie fish keeper in all of this. They are being stressed by their experience. They are dealing with new stuff they don't understand much about yet. A good attitude is not enough. I think it is as important not to panic folks at this stage. Telling folks that .25 ppm of total ammonia on their API kit is going to kill their fish or cause them grave injury when, in most cases, it will not do so, is sure not going to make them relaxed and help them not to mess up testing or dosing or changing water. Its really easy for us, who have been doing this for some time, to forget what nervous nellies we all were when we first started.
 
And I can't help myself, I have to fall back on the science (sorry only the abstract available):
 
Ammonia toxicity in fish

 

Abstract
 
Ammonia is present in the aquatic environment due to agricultural run-off and decomposition of biological waste. Ammonia is toxic to all vertebrates causing convulsions, coma and death, probably because elevated NH4+ displaces K+ and depolarizes neurons, causing activation of NMDA type glutamate receptor, which leads to an influx of excessive Ca2+ and subsequent cell death in the central nervous system.
 
Present ammonia criteria for aquatic systems are based on toxicity tests carried out on, starved, resting, non-stressed fish. This is doubly inappropriate. During exhaustive exercise and stress, fish increase ammonia production and are more sensitive to external ammonia. Present criteria do not protect swimming fish. Fish have strategies to protect them from the ammonia pulse following feeding, and this also protects them from increases in external ammonia, as a result starved fish are more sensitive to external ammonia than fed fish.
 
There are a number of fish species that can tolerate high environmental ammonia. Glutamine formation is an important ammonia detoxification strategy in the brain of fish, especially after feeding. Detoxification of ammonia to urea has also been observed in elasmobranches and some teleosts. Reduction in the rate of proteolysis and the rate of amino acid catabolism, which results in a decrease in ammonia production, may be another strategy to reduce ammonia toxicity. The weather loach volatilizes NH3, and the mudskipper, P. schlosseri, utilizes yet another unique strategy, it actively pumps NH4+ out of the body.

from http/www.sciencedirect.com/science/article/pii/S0025326X02002278
 
That is telling me that if you increase the level of stress (and/or activity) it makes fish more sensitive to ammonia in the water. That implies to me that lower levels of external ammonia from a water change may have a greater impact on a stressed from water change fish than pre-change levels would on the fish not stressed and with a lower internal ammonia level.

 

[eaglesaquarium]

I agree.  I just wish that LFS suggesting fish-in cycles would be more upfront about which fish are and aren't suitable.  Zebra danios are of course the poster children for cycling.  They seem to be the most capable of handling high ammonia and nitrite. 

 

[snazy]

snazy- you are comparing fish that have lived in your tanks for some time. You are not doing daily big water changes, you are doing weeklies I bet. Your fish have become used to water changes and are less upset by them. On the other hand fish going into a new tank from a fish store arrive not in the best shape. Then they go into a strange environment which is not relaxing either. I highly doubt if your fish today behave during a water change the same way they did when you performed their first few.
 

 
Yes, I agree and I actually try to do a water change prior to introducing new fish so they don't get stressed additionaly.
On another hand, when I cycled two tanks with Tetra safe start to test it after quite a bit of reading, I followed the instructions not to do water changes. I clearly remember the readings from the second tank as it was sooner(about 2 years ago) and it read 1ppm not moving up or down for 1 week. The nitrites spiked for just a couple of days and on day 8 the tank was cycled believe it or not.  It's not a good example but it's definately one showing fish can survive and live after being in some sort of ammonia.   I still have some of the fish that were in that tank(my common pleco, 4 of my albino corys and 1 of my red wag tail platies) Hence when I receive fish via the post I never worry about them spending another hour or so in some ammonia while the drip acclimating method clears that up via water removal. They can withstand that no bother. But the problem maybe when they are exposed for longer and higher levels of ammonia and nitrite, plus they do tend to die from diseases as a secondary thing rather than the ammonia itself, especially for fish that were just purchased and experience stress from new and possibly wrong enviroment, ammonia, new tank mates, possibly bullying tank mates, etc.. It's all about stress and ammonia is just one of the factors causing it.

 

[TwoTankAmin]

Once you added the Safe Start you changed the paradigm. Doing a water change soon after is throwing away what you just added. The only way to get the bottled bacteria to keep levels lower it to overdose it. They do not promise to cycle instantly, they promise your fish will make it basically. We have to assume that the bacteria in the bottle need time to revive and get into gear and then reproduce some. that is why they say about a week.
 
But what I suggest, if you have the time, is start to read the research on ammonia and nitrite toxicity. See what fresh were kept in what levels for how long and what the results were. If you read a fish lasted for 5 days at 2 ppm with not lasting damage, then you can probably figure it could do so at .25 or .5 ppm. And lets not forget that in the research there are two numbers- total ammonia and NH3. the damage tends to correlate to the NH# levels. And those numbers are usually on the -nitrogen scale.
 
Go to the toxicity charts. In a tank with a pH of 7.0, even at 85F, there is only .002 ppm of NH3. Even the most conservative number for the toxic levels of NH3 are at .02 ppm for the most sensitive of test subjects. I work with a number closer to .05. A pH of 7.8 and a temp of 80F and a test reading of .5 ppm would give one .02 ppm of NH3.
 
And lastly, given all you have seen and read about ammonia testing and the reliability of low level readings, how sure are you of that a reading of .25 or .50 ppm on most kits may actually be accurate?
 
So why do any of us use ammonia kits if they are not good at low levels? Because we have a better chance to spot the NH3 that way. It is a lot easier to spot .25 or .5 ppm total ammonia than .02 - .05 ppm of the really harmful NH3. And at higher levels they give us a way to know what direction levels are moving. 2 ppm looks different moving up vs down from it.
 
What has happened is the hobby is essentially applying the total ion scale to assess levels given in term of the nitrogen scale.
 
But here is another interesting study on the effects of ammonia on tilapia over 2 days. Without more details here are the ammonia levels used: "Ammonia stress was induced by adding ammonium chloride to each aquarium to achieve TAN concentrations of 2.0, 12.0, 40.0 mg/L. At the beginning the pH was maintained at 6.9±0.1 for about 120 min to act as a reference and corresponding UIA concentrations of 0.008, 0.048, 0.159 mg/L respectively. Sodium hydroxide solution was added gradually into the water to increase the pH to 8.1±0.1 during a period of about 20 min, accordingly UIA concentrations increased to 0.13 (low), 0.79 (moderate), 2.65 mg/L (high) level."
full study from http/www.ncbi.nlm.nih.gov/pmc/articles/PMC1389864/
 
So above I discussed toxic levels of NH3 starting at .05 ppm. The experiment exposed fish to 3 levels of this- .13, .79 and 2.65 ppm. They had some fish in 40 ppm total ammonia nitrogen/TAN (about 51 ppm on an API kit) for two days. How can one argue that .25 ppm of total ammonia is going do bad things to fish fast when 200+ times that level won't kill some in 48 hours? The purpose of the study was to see is fish behavior would signal ammonia stress, it did: Behavioral response of tilapia (Oreochromis niloticus) to acute ammonia stress monitored by computer vision.
 
The danger during acclimation isn't rising ammonia, its a conversion of the existing ammonia into more of the toxic NH3 form due CO2 out gassing and O in gassing. That shifts the balance between NH4 and NH3 more towards the latter as the pH rises.

 

[TwoTankAmin]

Yoohoo snazy, where are you?
 
I wanted to have a chance to show your speculation about biofilms and where the nitrifying bacteria live in a tank was something you apparently made up and which you could not support with any science. But aside from that I wanted you to explain to us all the science behind your statements about the toxicty of ammonia. I expected you to at least to respond to the accusation that I cherry pick by picking anything you wanted to the contrary to cite in support of what you say. Can you show any research on the effect of exposure to NH3 at levels under .05 ppm in the months after the end of a study?
 
I would have responded to the cherry picking notion in the original thread, but we had already hijacked it enough. So I will do it here where those interested can follow and read or not as they choose. There are many studies, articles and books available on this topic. But as one plods through the mountain of information a lot of it is difficult to relate to aquariums. If I post a study about ammonia and cold water fish, I get told these fish are not in tanks. So I do try to find information more appropriate. I also tend to restrict what I cite to things published from 2000 to present to avoid the criticism that the info is dated. Finally, I try to restrict the information to those studies for which the whole text is available for no charge. So to this extent, yes I cherry pick.
 
Effects of ammonia on juvenile silver perch Bidyanus bidyanus/
http/elmu.umm.ac.id/file.php/1/jurnal/A/Aquaculture/Vol183.Issue1-2.Mar2000/61096.pdf
 
Chronic ammonia toxicity to duckweed-fed tilapia (Oreochromis niloticus)
http/www.bvsde.paho.org/bvsacd/leeds/chronic.pdf
 
Tolerance to temperature, pH, ammonia and nitrite in cardinal tetra, Paracheirodon axelrodi, an amazonian ornamental fish
http/www.scielo.br/pdf/aa/v38n4/v38n4a23.pdf
 
Acute toxicity and sublethal effects of ammonia and nitrite for juvenile cobia Rachycentron canadum
http/www.sciencedirect.com/science/article/pii/S0044848607004838
 
The Merck Veteinary Manual for Veterinary Professionals
http/www.merckmanuals.com/vet/exotic_and_laboratory_animals/fish/environmental_diseases_of_fish.html?qt=&sc=&alt=
(scroll down to Nitrogenous Compounds)
 
Effects of diel un-ionized ammonia fluctuation on juvenile hybrid striped bass, channel catfish, and blue tilapia
http/www.sciencedirect.com/science/article/pii/S0044848600005433
(Sorry, abstract only)
 
Influence of pH, Salinity, Calcium, and Ammonia Source on Acute Ammonia Toxicity to Golden Shiners, Notemigonus crysoleucas
http/www.sciencedirect.com/science/article/pii/S0043135411007639
(Sorry, abstract only)
 
RATIONALE FOR THE ESTABLISHMENT OF ONTARIO'S PROVINCIAL WATER QUALITY OBJECTIVES
http/agrienvarchive.ca/download/rationale_watqual_obj1979.pdf
(Older paper from 1979- scroll down to page 11)
 
Here is one which is so technical none of us here will thoroughly understand it. But when you hit the conclusion paragraph it isn't so tough.
Oxidative stress and antioxidant enzymes in liver and white muscle of Nile tilapia juveniles in chronic ammonia exposure
http/www.academia.edu/download/31062196/ScienceDirect_-_Aquatic_Toxicology__Oxidative_stress_and_antioxidant_enzymes_in_liver_and_white_muscle_of_Nile_tilapia_juveniles_in_chro.pdf
(They exposed fish to 5 ppm and 10 ppm of total ammonia nitrogen for 70 days, I talk about exposing fish to 1-2 ppm (API kit) for a week or two and the final line of the study states: "The level of ammonia used in the present experiment is not enough to crash the antioxidant enzymes system in Nile tilapia." Bear in mind the deifferent scale used by API kits- 5 ppm TAN= 6.4 ppm, 10 ppm = 12.8 ppm on an API Kit)
 
Accumulation of ammonia in the body and NH3 volatilization from alkaline regions of the body surface during ammonia loading and exposure to air in the weather loach Misgurnus anguillicaudatus
http/jeb.biologists.org/content/205/5/651.full
 
Dogmas and controversies in the handling of nitrogenous wastes: Is exogenous ammonia a growth stimulant in fish?
http/jeb.biologists.org/content/207/12/2043.long
(Sorry, I have trouble converting μmol to ppm, can anybody out there convert total ammonia concentrations ([TAmm])=0, 70 and 225 μmol l–1 to ppm/)
 
Now I know what some folks will respond, these are often studies in lethality, or they are short terms periods like 96 hours or they are not all fish we might keep in tanks, or its just one fish and doesn't generalize. . To which I would respond on several levels.
 
1. Most of the studies involved are looking at much higher levels of ammonia than I would ever state are allowable in a tank undergoing a fish in cycle. It is difficult to find studies dealing specifically with NH3 levels under .05 ppm or TAN under 2 ppm and short term exposure times typical of cycling.
2. The longer term studies cover periods much longer than the typical exposure times and levels one should experience in a proper fish in cycle.
3. The stress levels for fish in healthy aquariums (in terms of stocking and parameters such as GH, pH etc) is nowhere near what they are in the wild.
4. Most of the studies will reference the importance of not only the ammonia levels but also the duration of exposure. These are both critical factors.
5. The apparent agreement across many studies of what constitutes the danger levels and exposure times would seem to more than mere coincidence.
6. Very few studies follow the subject fish after the study is done. So there is a dearth of available data on this. How well do fish recover from damage which may be caused by lower level short term exposure to ammonia?
7. We have to draw conclusions from the preponderance of the evidence available and work with that.
 
My point is all of this is that to understand the potential effects of ammonia on fish being used to conduct a fish in cycle, one must consider the ammonia levels involved, the other parameters that determine the NH3 and NH4 components in water and the exposure time. Then one need to consider the species of fish involved and their life stages.
 
Finally, I would like to have anybody explain to me this. Start with the assumption that 3 ppm of total ammonia is an adequate level to use in a fishless cycle to enable one to stock fully when the cycle is done. We work to hold the levels here and maintain that ammonia level. But in a fish in cycle the proper protocol is to start with a small bio-load, cycle for that and when it has been done, add more fish in a way that doesn't over load the bio-filter.
 
If the load used in stage one of a fish in cycle is just 1/3 of the final stocking in a fishless cycle, shouldn't the system only need to process just 1 ppm of ammonia in 24 hours rather than the 3 ppm used in fishless? What are the implications of this? How about if you are doing it correctly, that you allow the ammonia levels to rise a bit over 1 ppm before taking action to bring them down under 1 ppm? Especially, if you determine that the level of NH3 in that 1 or so ppm is clearly under .05 ppm.
 
And then consider the second important component in ammonia exposure, after concentration, duration of exposure. Common sense should tell us that it takes less time to grow enough AOB to process 1 ppm of TAN in under 24 hours than it does to grow enough AOB to process 3 ppm in that time period. So this means the amount of time fish need to be exposed to that 1 odd ppm of TAN should be less than that of fishless cycling or the old way of letting ammonia just rise during fish in.
 
The traditional fishless cycling chart that is still being used today is below. Note that it is in -nitrogen which makes the peaks lower than they would be on the total ion scale common with test kits. It shows a peak well over 10 ppm of ammonia and a a total exposure time to any level of ammonia of about 3 weeks.
 

 
By letting the allowable ammonia levels to rise to somewhere in the 1-2 ppm range during fish in cycling, it should shorten the days of exposure. So we now are working at significantly lower concentrations and/or durations than most of the research into ammonia toxicity does.
 
There is a huge difference in having fish exposed to ammonia during a fish in cycling vs having ammonia show up in an established tank. We want and need ammonia present during a fish in cycle, without it there is no cycle. So the presence of ammonia in a fish in cycle is an indication that cycling is going right. In a healthy tank, there should be no detectible ammonia, so its presence is an indication that something is wrong and must be addressed ASAP.
 
An even more interesting idea to consider is what happens if one cycles with fish properly and is able to seed some bacteria into the tank at the outset? Given the low level of ammonia involved and how short exposure might already be, a small amount of seeding could have a pretty big impact. The key is to start at the low load or if one has started with too many fish, to remove some. The art of fish in cycling has apparently been forgotten with the prevalence of fishless.
 
The idea that doing big water changes as often as I see suggested so often on this and other forums itself is a stressor of fish doesn't ever seem to figure into this advice. There is a tradeoff between the ammonia levels and the duration relative to stress. If one wants to suggest changing water every time ammonia reaches .25 or .5 ppm during a fish in cycle even when the NH3 component is under .05 ppm, I would ask you to show me some evidence that the extended time this necessitates at lower level exposures combined with the additional stress of all the water changes is less harmful to the fish in the long run than what I propose.