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Old 03-08-2014, 07:15 PM   #1
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Nitrite toxicity discussion

I've been doing some research on some scientific papers regarding the toxicity of nitrite to fish. Granted I haven't found many papers and there doesn't really seems to be any conclusive studies on this topic.

In the link I will provide the conclusions I have gathered are that nitrite toxicity is completely dependent on species and size of fish. Also amounts of chloride and bicarbonate present in the environment and levels of dissolved oxygen.

The article also describes how fish have a natural mechanism or reductase cells that reverse the formation of methemoglobin as it is accumulating. The lethality of nitrite is dependent on how well the species can do this. It also says that all fish have some levels of methemoglobin present in the cells as a percentage and that the starting percentage is dependent again on species.

There is also a chloride offset. My tap water report shows I have 5.85mg/l of chloride and I worked out that this would offset nitrite by around 2-2.5ppm according to this page.
If taking in to consideration the size of my fish and the species (impossible to study all species) and their background methemoglobin (percentage of meth already in cell) coupled with the ability of the species reductase cells to reverse the process. This could explain why some people have experienced elevated levels if nitrite with no consequence.

I'm still trying to figure out what levels of nitrite would be considered dangerous. This link seems to suggest nitrite levels of 1ppm upwards. But with everything else mentioned taken in to consideration I don't think it would come as a surprise to me that in some cases aquarium fish have survived higher concentrations.

I would always encourage people to change water in the event of nitrites and I'm not saying that it should be taken any less seriously. I was just wondering what your thoughts were and if you had any other papers that would provide an interesting read.

If fish in cycles are constantly reading levels of 0.25ppm on an API master test kit for example that would equate to around 0.6ppm nitrite. After 2 days the accumulation would already be over 1ppm nitrite early in the cycle but my fish never shown any distress.

I just find this interesting. It's difficult to know if nitrite accumulation has caused a fishes death because you would need ammonia which would most likely do the damage first.

Here the link http://ciresweb.colorado.edu/limnolo...dfs/Pub079.pdf

Feel free to blow my thoughts out of the water or add anything else.
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Old 03-09-2014, 04:33 AM   #2
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I haven't read ANY of these but here are my bookmarks on this topic.

http://www.aces.edu/dept/fisheries/a...BrownBlood.pdf
Recent advances in fish toxicology: a symposium - Corvallis Environmental Research Laboratory, United States. Environmental Protection Agency. Office of Research and Development - Google Books
http://www-heb.pac.dfo-mpo.gc.ca/con...94/tomasso.pdf
http://actavet.vfu.cz/pdf/200574010129.pdf
http://www.agriculturejournals.cz/publicFiles/61325.pdf

Here are some studies all about Danios, our favorite hardy cycling fish:
http://actavet.vfu.cz/pdf/200675010107.pdf
http://actavet.vfu.cz/pdf/200574030435.pdf
http://actavet.vfu.cz/pdf/200877030455.pdf
http://actavet.vfu.cz/pdf/201180030309.pdf
Nitric oxide formation from nitrite in zebrafish



Have some reading material!
I will get started on these :P
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Old 03-09-2014, 04:53 AM   #4
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http://www.aces.edu/dept/fisheries/a...BrownBlood.pdf
First article

This one has interesting info on nitrite toxicity protection by sodium chloride (table salt). We've heard of this before, but this one offers that the fish are protected at a ratio of 9:1 sodium chloride to nitrites. Meaning for every 1ppm nitrites, you need 9ppm sodium chloride in order to protect the fish.
I've seen other papers that provide a "maximum" protected level that sodium chloride can protect to (and after that the nitrite is just toxic), but this particular paper just stresses the 9:1 ratio. Its example problems use 8ppm nitrite to calculate 72ppm salt for protection.
It's also worth noting that they simply talk about table salt and not some fancy aquarium salt, although I would venture you would want to use iodine-free. I know that a lot of the old-timers poo-poo the whole "aquarium salt" thing and it really does seem to be a fancy repackaging of the same old thing.

"Farmers who routinely maintain a minimum of 60-150 ppm of chloride in water at all times seldom experience losses from nitrite build-up and effectively prevent nitrite poisoning"
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Old 03-09-2014, 04:53 AM   #5
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Quote:
Originally Posted by Caliban07 View Post
Your search engine is better than mine lol.

I have a whole lot of reading to do. Thanks threnjen.
I just have mad research skillz
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Old 03-09-2014, 05:25 AM   #6
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Question: Is nitrite dangerous to fish SOLELY because it reduces oxygen in the blood and makes them suffocate?

On another note:
I wanted to know how much table salt was required to increase to 100ppm. I filled a 1 gallon jug (3.79L) with my tap water. I used my TDS meter to check dissolved solids (18ppm). I added 1 tsp salt (about 6g). TDS was then 208, so even that was overkill. It's approximately 1/2 tsp per gallon, or 3g per gallon, or 4g/5L to add 100ppm sodium chloride.

This is all approximate, I grabbed my not-most-accurate scale. I actually have a scale that goes to hundredths of a gram but I was too lazy to grab it. If we come up with some actual recommendation for the newbies I will use it to get a more accurate reading.

It would honestly be really helpful to be able to confidently assert to the fish-in people that they should add salt during the nitrite phase.
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Old 03-09-2014, 06:01 AM   #7
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Quote:
Originally Posted by threnjen View Post
Question: Is nitrite dangerous to fish SOLELY because it reduces oxygen in the blood and makes them suffocate?

On another note:
I wanted to know how much table salt was required to increase to 100ppm. I filled a 1 gallon jug (3.79L) with my tap water. I used my TDS meter to check dissolved solids (18ppm). I added 1 tsp salt (about 6g). TDS was then 208, so even that was overkill. It's approximately 1/2 tsp per gallon, or 3g per gallon, or 4g/5L to add 100ppm sodium chloride.

This is all approximate, I grabbed my not-most-accurate scale. I actually have a scale that goes to hundredths of a gram but I was too lazy to grab it. If we come up with some actual recommendation for the newbies I will use it to get a more accurate reading.

It would honestly be really helpful to be able to confidently assert to the fish-in people that they should add salt during the nitrite phase.
Interesting stuff. There was a bit that mentioned calcium can increase the effect of chloride also. still I added 0 salt during my fish in cycle and my fish were ok. I didnt observe any reading of nitrite although testing was sporadic. It will be interesting to read the danio paper as this will be closer to the species we are used to seeing in our aquarium. I agree salt during a fish in that has gone wrong would be recommended so far. And maybe the addition as a preventative would aslo be helpful.

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Old 03-09-2014, 06:06 AM   #8
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The 96hLC50 for smaller fish (average weight 4.4 ± 1.50
g) was 266.17 mg·l-1 NO2- and larger fish (90.7 ± 16.43 g) demonstrated 96hLC50 of 26.29 mg·l-1 NO2-. Nitrite doesnt come close to these levels in our aquariums

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Old 03-09-2014, 06:22 AM   #9
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Did you read the one about danios and guppies? The danios had really high resistance like 250+ but the guppies were around 20. That water had a bunch of NaCl added to it to protect them.
I haven't read all the papers yet,been distracted.

I didn't realize that NaCl was so important. That original paper you posted is one I have read before but I see now that basically ALL of the papers advocate NaCl addition to protect from toxicity.
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Old 03-09-2014, 06:24 AM   #10
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The first of the danio links has a graph. The tested 20-25 day old danios against 2-3 months old danios.

Chloride levels at the lowest level of 19mg/l indicated that the 96 hour mean lethel concentration was near the 200mg/l mark

Thats a lot of nitrite needed to kill half the danio population.

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