Hi everyone, I'm tossing this info out as an FYI. I had originally posted to an old thread in General, but it was pointed out that this would be more useful in its own thread elsewhere, so here it is! It absolutely chills me to think that misinformation about nitrate is out there. :S There are a number of studies that have examined the health consequences of chronic, high-level nitrate exposure to fish. I will link to publicly accessible pages that are free for anyone to access.
The study that I am most familiar with (and I think easiest for most people to read) used water with nitrate added (to rule out effects of other factors like temperature and hormones) to evaluate its health effects on hybrid striped bass exposed to the equivalent of 200 ppm nitrate for a /month/ versus a control group. The exposed fish had reduced immune response, reduced antibody counts, anemia from red blood cell lysis, jaundice, kidney failure, and some symptoms that mimicked blindness despite no visible lesions on the fishes' eyes. If you would like to read the original paper, it can be found here. http://www.atlantech.ca/public/artic... Quality.PDF 10-20 ppm appears ideal, with 40 ppm being the absolute upper limit that you should tolerate your tanks being at. (Hint: for most purposes, ppm is the same as mg/mL).
This may raise the question of what values are fish exposed to normally? What do they LIVE in? Here's some numbers taken from rivers and standing bodies of water in New Zealand -- 88 ppm appears to be upper limit of more polluted waters (acute exposure for 4 or less days!), while most other areas where fish and humans share water range between 4.4 to 16 ppm (multiply those numbers by 4.4!) http://ecan.govt.nz/publications/Re...ity-freshwater-aquatic-species-000609-web.pdf
Another paper summarizes all the different research that's been done on nitrate toxicity to fish, amphibians, and invertebrates. The toxicity values are listed on Table 3, page 1261. The LOEC (Lowest Observed Effect Concentration) is the smallest concentration at which negative effects can be observed in ANY fish (trout are pretty sensitive to water quality). You may also happen to notice some REALLY HIGH numbers! Don't kid yourself though, those are concentrations of nitrate that will KILL half of all fish exposed to it for that period of time (LC50, for 24 hours). http://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_2/2008/ref2426.pdf
Bottom line: 0-10 ppm nitrate is ideal, 20 is okay, and you'd better be doing a water change at anything over 40 ppm. I hope this helps, and if you ever find yourself arguing with anyone else about it, feel free to link to this thread.
The study that I am most familiar with (and I think easiest for most people to read) used water with nitrate added (to rule out effects of other factors like temperature and hormones) to evaluate its health effects on hybrid striped bass exposed to the equivalent of 200 ppm nitrate for a /month/ versus a control group. The exposed fish had reduced immune response, reduced antibody counts, anemia from red blood cell lysis, jaundice, kidney failure, and some symptoms that mimicked blindness despite no visible lesions on the fishes' eyes. If you would like to read the original paper, it can be found here. http://www.atlantech.ca/public/artic... Quality.PDF 10-20 ppm appears ideal, with 40 ppm being the absolute upper limit that you should tolerate your tanks being at. (Hint: for most purposes, ppm is the same as mg/mL).
This may raise the question of what values are fish exposed to normally? What do they LIVE in? Here's some numbers taken from rivers and standing bodies of water in New Zealand -- 88 ppm appears to be upper limit of more polluted waters (acute exposure for 4 or less days!), while most other areas where fish and humans share water range between 4.4 to 16 ppm (multiply those numbers by 4.4!) http://ecan.govt.nz/publications/Re...ity-freshwater-aquatic-species-000609-web.pdf
Another paper summarizes all the different research that's been done on nitrate toxicity to fish, amphibians, and invertebrates. The toxicity values are listed on Table 3, page 1261. The LOEC (Lowest Observed Effect Concentration) is the smallest concentration at which negative effects can be observed in ANY fish (trout are pretty sensitive to water quality). You may also happen to notice some REALLY HIGH numbers! Don't kid yourself though, those are concentrations of nitrate that will KILL half of all fish exposed to it for that period of time (LC50, for 24 hours). http://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_2/2008/ref2426.pdf
Bottom line: 0-10 ppm nitrate is ideal, 20 is okay, and you'd better be doing a water change at anything over 40 ppm. I hope this helps, and if you ever find yourself arguing with anyone else about it, feel free to link to this thread.
) I'm sure there will be some dissent and people will readily point out numbers are different for different species, but it doesnt have a rule of thumb to stick to. I usually try to keep my nitrates below 30, but they usually hit around 40 before I can do a water change. After reading these articles I think I will be finishing my stand and adding pothos sooner than I thought
