I am sorry for the length of this post. But sience is rarely something that can be explained in a few words. What is mosre important, imo, it that what Colin said and I quote below will likely cause more harm than good in terms of nitrite. This will be explained by what follows.
Salt (sodium chloride) is not a fix for nitrite poisoning. It's a band-aid solution to stop the fish being filled with nitrogen when people can't be bothered doing water changes. Diluting nitrite is much better for the fish than adding salt.
This is 100% not the case. And there are two major reasons it is wrong. Colin has not been doing his homework, I fear.
The first reason has to do with cycling related issues and fixing the problem of there being nitrite. The solution is to increase the bacteria that handle nitrite and convert it to nitrate. Let us start with the fact that both the ammonia and nitrite bacteria have some number of individual cells in a colony die every day. At the same time they also have some number which reproduce by dividing.
When there are a sufficient number of nitrite bacteria in the tank, this results in 0 nitrite being detected by our kits. As long as the nitrite output in the tank reamins fairly steady, the size of the bacteria colonies of nitrite oxidizers will also be steady. But, If we were to remove a number of the fish in the tanks, the result would be to lower the amount of nitrite being created. In response, the death rate will be steady but the rate of cell division will not b., It will be reduced or even close to stopped until the colny size shrinks back to be in balance with the available nitrite .
If more fish are added to the tank, the amount of nitrite being created will increase and the reverse will happen. The death rate stays steady but the birth rate will increase until once again the size of the colony is big enough to handle the nitrite. This process is the same for ammonia.
So the goal is to fix any imbalance resulting from elevated ammonia or nitrite is to have the needed additional bacteria get created ASAP as long as the fish are being kept safe. When it comes to ammonia there are only a few options. One is water changing. Another is adding chemicals which are ammonia detoxify agents. What these tend to do is convert ammonia (NH3) to a less harmful form. The bacteria can still use this, but not as efficiently as they can use NH3. The result is they will reproduce more slowly. That means ammonia will likely persist for longer.
Water changing for ammonia lowers the ppm in the water. And this too slows the reproduction rate for a short time. But the ammonia will have to rise again as it is still being created and there are still not enough bacteria to control it. Unfortunately, either option will extend the length of time it will take to have the problem controlled and thus eliminated.
There is one factor at work here which has to do with the reproductive rates of the two bacteria. Under optimal conditions the ammonia bacteria need at least 8 hours to double their numbers. The nitrite ones are slower and need more like 12-13 hours. However, it is very rare to have optimal conditions in a tank. So the time needed to double will be a lot longer.
Since we are talking about nitrite here lets just focus on that. Due to the differing doubling times, there comes a pointwhen the ammonia will be under control but the nitrite will not. And if one has to do water changes for ammonia it will lower the level of that and of the nitrite. So both will still be there, but in lower concentrations. The fish have no defense against ammonia and even at lower levels it can cause problems. Nitrite is another story.
Once nitrite is inside a fish it takes around 48 hours or more to work it's way out. But, if there is still nitrite in the water, it will continue entering a fish and it can accumulate. But unlike with ammonia, there is a way to prevent nitrite from even entering a fish. Add that is chloride in the water.
Sodium chloride (common salt, NaCl) is used to “treat” brown blood disease. Calcium chloride can also be used but is typically more expensive. The chloride portion of salt competes with nitrite for absorption through the gills.
Maintaining at least a 10 to 1 ratio of chloride to nitrite in a pond effectively prevents nitrite from entering catfish. Where catfish (or other fish) have bacterial and/or parasite diseases, their sensitivity to nitrite may be greater, and a higher chloride-to-nitrite ratiomay be needed to afford added protection from nitrite invasion into the bloodstream.
from
Nitrite in Fish Ponds
The below is from the Merck Veterinary Manual
NO2 toxicity can be rapidly corrected by a water change, but this may not be practical for large ponds. Increasing chloride (Cl–) concentration in fresh water systems is another solution: Cl– serves as an antagonist for NO2 at the gill epithelium. Many ornamental ponds and aquaria are maintained with residual chloride levels because of the addition of salt (1–3 ppt) as a relatively permanent treatment. In these cases, NO2 toxicity is less likely to be a problem, because chloride levels are increased by the residual salt concentration and competitively block NO2 absorption. In freshwater production ponds for channel catfish, low concentrations of salt can be used to provide sufficient environmental chloride to mitigate the risk of methemoglobinem is caused by sudden increases in NO2.
https://www.merckvetmanual.com/exot...ment for fish#Nitrogenous-Compounds_v23353503
One more thing, the scientific community has stated that any research done involving nitrite and fish must contain information about chloride levels int the water. Lacking this causes the research to be considered mostly worthless. Here is how the Google AI puts it
AI Overview
Learn more
Research papers on nitrite and fish that lack chloride data are of limited value because chloride plays a crucial role in mitigating nitrite toxicity in fish, meaning the results may not accurately reflect the full impact of nitrite exposure in a natural aquatic environment; essentially, the absence of chloride information can significantly undermine the study's reliability when assessing nitrite toxicity to fish.
What all of the above means is that the best way to protect a fish from nitrite is by using a proper level of cloride in the water which prevents the nitrite from entering the fish. Water changes are absolutely not the way to protect fish from nitrite, chloride is.
This is easy to do especially when the ammonia is not an issue. And even if ammonia is the concern and one changes water to handle it, this just means you need to add less chloride to protect fish. The easiest, cheapest and most available way to do this is with plain old salt, the kind we put on our food- NaCl- sodium chloride.
The best part of this is that the amount of salt it takes to produce sufficient chloride to block most concentrations of nitrite we might see in tanks is not enough salt to harm almost any fish. Different sources may suggest somewhat different levels of chloride are needed to combat x ppm of nitrite in the water. All you have to do is read the second Rescuing a Fish in Cycle Gone Wild (which I wrote for this site about 11 years ago). It has a step-by-step guide for calculating how much salt I suggest to add to produce the amount of chloride one should add based on their actual ppms of nitrite and the volume of water in the tank.
The final benefit of avoiding an ammonia detoxifier, if possible, is it slows the completion/restoration of the cycle. On the other hand, the salt added for its chloride content will not slow the cycle, the bacteria can still reproduce at the same speed as they would without salt present. The ammonia ones are slowed by the process which renders a tank safe from ammonia under most ot the conditions we might encounter in our tanks.
So, when Colin posted what he did about using water changes instead of using chloride in the water, it was not exactly the best thing we can learn to do if we have to handle nitrite in our tanks with fish in them. We can not render ammonia harmless by preventing it from entering the fish via the gills the way the chloride can do for nitrite.
Chloride is a fix for nitrite poisoning because nitrite will naturally come out of the fish. So, if no more can enter, in a few days the nitrite is gone from the fish. There is one thing that can actually counteract nitrite inside a fish. But it is not usually practical to use for treating a whole tank, especially a display type tank. That is to add methylene blue. But it will stain many things in the tank, especially silicone. Plus the cost of M B v.s. salt is substantial especially of one has a decnt size tank.
Here is what Fritz says about methylene blue which they sell (bold added by me).
To aid in general disease prevention, detoxification of fishes suffering from nitrite or cyanide poisoning and for use as a prophylaxis against fungus infections of fish spawns (eggs), add 10 drops per gallon (3.78 liters) or 1 teaspoon per 10 gallons (37.8 liters) of water (this will result in 3 ppm Methylene Blue). Discontinue carbon filtration but keep all other filtration running during treatment. Replace carbon after treatment.
from
https://fritzaquatics.com/assets/files/uploads/Y6R5D-ProMethyleneBlue.pdf
It there is no ammonia but there is nitrite in a tank, doing water changes will actually be bad for the fish. It will extend the time needed to get the required amount of bacteria by slowing the bacterial reproduction. Without the chloride, more nitrite will enter the fish as long as it is in the water. So only doing water changes will insure some level of nitrite poisoning in the fish will be prolonged.
I do not want anybody to think there is limited research on this subject. So here is a link to the results of my search on Google Scholar for "prevention of "Nitrite" poisoning in fish" which I had to limit to only the 10 years 2015-2024 to keep the studies down to 8,880 responses. (Left unconstrained for time you get about 18,500 results.)
https://scholar.google.com/scholar?...evention+of+"Nitrite"+poisoning+in+fish&btnG=
I have not read them all and neither should you but you might find it informative to look into a few.
Now, I invite Colin to give us more than a few words to support what he wrote. I am happy to read at any science he offers which support it. I am willing to peruse a number of the studies and research he offers and to compare it to what I offered. And, if I am wrong, I will say so publicly and offer an apology as well. Otherwise I would expect him to alter his thinking and what he posts in this regard.. New keepers on the sitemay take it to heart. t
I have nothing against Colin as a person. What I object to is he posting of what I strongly believeto be poor advice and which I believe is likely to be harmful to fish.
