Maximum Safe Nitrate levels for fish?

[wh33t]

Hello all,

I've just got my Nitrate test kit and I'm curious as to see what kind of readings I should want to get?

I've got 8 gold fish so it would be great to know the maximum safe level for them but I would love to be able to look up that kind of information as well, is there any way to do that?

[keith_r]

you'll probably hear different opinions... i would be worried if they were above 200

[rfeiller]

i find mine do better at 100 then 200. if you have sufficient grow beds it shouldn't hit 200.

[urbanfarmer]

For catfish to die after 4 days it takes 6,200 mg/L or 6,200 PPM Nitrate. I am still looking for goldfish, but it looks like no one cares what level of nitrate is unsafe for goldfish. This could be because there's no economical benefit to be gained from researching it or the nitrate required is too high (or non at all) that affect the fish. I will post if I find anything closer. For Tilapia the level of nitrate would be even higher than that (basically it can be said it's non-toxic to Tilapia).

Evaluation of the short-term toxicity of nitrogenous compounds to channel catfish, Ictalurus punctatus
aDepartment of Civil Engineering, University of California at Davis, Davis, Calif. 95616 U.S.A.

Abstract
The acute toxicity of un-ionized ammonia, nitrite, and nitrate to 50–76-mm fingerling channel catfish (Ictalurus punctatus) was investigated using a static bioassay system at 22, 26 and 30°C. The 96-h LC50 values at 30°C for un-ionized ammonia, nitrite, and nitrate were 3.8, 44, and 6 200 mg/l.

[urbanfarmer]

This study was interesting to me because it actually contradicts what most online fish folks state, that nitrate levels cause a decrease in fish growth. Nitrate levels do not affect thyroid function, at least in these fish species.

Uptake and distribution of radioiodine, and the effect of ambient nitrate, in some fish species.
Comp Biochem Physiol A Comp Physiol. 1985;80(3):337-42.

[urbanfarmer]

I have several books on aquaculture that clearly state nitrate is non-toxic to fish in general. I know that may be too vague for your needs, but if anyone can show some evidence to the contrary I would (as usual) absolutely love to read it. I look through journals with these kinds of keywords, and it's really hard to find much of anything on the topic: nitrate toxicity LC50 Carassius auratus goldfish

I used several combinations of those terms to try to pull up anything stating nitrate is or is not toxic or of it is at what level... I can't find much.

[rfeiller]

The stunting is caused by the concentration of hormonal secretion of the fish. There are several factors that happening. In a closed system. All aquaponics is only concerned with nitrates. There are fish such as catfish that can exist in a high concentration of sewage. A number of tilapia are from a dead end water system in Africa called the rift river valley system an they have adapted to extreme conditions. Not so for many fish species.
Along with a higher concentration of nitrates is a higher concentration of pathogens and parasites.

[urbanfarmer]

The stunting is caused by the concentration of hormonal secretion of the fish. There are several factors that happening. In a closed system. All aquaponics is only concerned with nitrates. There are fish such as catfish that can exist in a high concentration of sewage. A number of tilapia are from a dead end water system in Africa called the rift river valley system an they have adapted to extreme conditions. Not so for many fish species.
Along with a higher concentration of nitrates is a higher concentration of pathogens and parasites.
Well, aside from the toxins, there are many factors that can stunt fish growth including temperature. However, nitrate, from my experience and research, is not one of them.

As far as the hormonal secretion stunting growth, sure it exists in some fish (I want to say it's rare). I have had to specifically search for fish that do this, and I can't even remember the species, but needless to say I don't think goldfish, tilapia, or catfish are among those that do. There's a lot of folklore and BS out there on the topic, but the sience doesn't back it up... and, unfortunately, a lot of us have read that junk and taken it as gospel.

[badflash]

Goldfish are carp. I don't think you can get to a toxic level unless you add miracle grow. Keep the particulates and nitrites and ammonia under control and you should be good, but don't stick with goldies. Move up to koi or catfish once you've figured out how to handle your water.

[keith_r]

The main toxic action of nitrate on aquatic animals is
due to the conversion of oxygen-carrying pigments (e.g.,
hemoglobin, hemocyanin) to forms that are incapable of
carrying oxygen (e.g., methemoglobin) (Grabda et al.,
1974; Conrad, 1990; Jensen, 1996; Scott and Crunkilton,
2000; Cheng and Chen, 2002). Nevertheless, owing to
the low branchial permeability to nitrate, the NO

3 uptake
in aquatic animals seems to be more limited than
the uptake of NHþ
4 and NO

2 , contributing to the relatively
low toxicity of nitrate (Russo, 1985; Meade and
Watts, 1995; Jensen, 1996; Stormer et al., 1996; Cheng
and Chen, 2002; Alonso and Camargo, 2003).

from
http://www.waterboards.ca.gov/water_iss ... ef2426.pdf (http://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_2/2008/ref2426.pdf)

there's a newer study out on nitrate toxicity in fish, but i ain't shellin out 41 bucks

[urbanfarmer]

Methemoglobinemia, more commonly called brown blood disease (which we have discussed in detail in other posts), can happen to most living organisms if nitrate gets in the blood stream. The question remains at what concentration in water does nitrate pose a threat to fish, specifically the ones we're interested in culturing. The study lists some species at different stages of development.


Nitrate toxicity to freshwater and marine fishes increases
with increasing nitrate concentrations and exposure
times (Trama, 1954; Westin, 1974; Colt and
Tchobanoglous, 1976; Rubin and Elmaraghy, 1977;
Kincheloe et al., 1979; Brownell, 1980; Tomasso and
Carmichael, 1986; Pierce et al., 1993; Scott and Crunkilton,
2000). Furthermore, nitrate toxicity can depend
greatly upon the cationic composition of the solution
(Dowden and Bennett, 1965). As in the case of aquatic
invertebrates, freshwater fishes appear to be more sensitive
to nitrate toxicity than marine fishes.

Well this is getting complicated. And Tilapia are capable of both freshwater and marine environments! What is also interesting is this study would lead you to believe that all fish have low tolerances for nitrate the younger they are up to being an egg; however, Tilapia eggs are impervious to nitrate and even ammonia meaning they have no toxicity at that stage of development either.

Also, it has been my observation the feeder goldfish are raised in such poor conditions that the ones that survive are quite adapted to high nitrate, nitrite, and ammonia levels. They have been Darwinized to have good genetics for this kind of thing.

Anyway, this is pretty amazing data and there's quite a bit of it. Thank you for sharing. It's going straight into my archives! :ugeek:

[keith_r]

welcome
it is complicated, thats for sure, especially when you can find contradicting information on just about any subject...
gotta look at who's funding the study, as well as the goals.. AP is still incredibly new and isn't really a "proven" technology in any mass markets... gotta watch out for aqua scheister's..
i was recently reading a study on the stunting of fish, and the initial findings suggested that overcrowding and inappropriate diet had more to do with stunting than any hormonal secretions,
but like i said, you can probably find more studies saying it's hormonal..

[urbanfarmer]

The thing about saying it's hormonal is they identify the hormone, look at it, run tests/research to show experimentally that the theory also matches the observations. However, no such hormone has been found for most the species I have looked into. I would imagine the lack of glands/organs and lack of physiological evidence would suggest it's not even likely the hormones are produced in certain species. It's like trying to say there's a needle in the haystack when we have a very fine tuned metal detector and it's coming up with nothing... anyway, maybe there's such a mechanism yet undiscovered, but we know it's not the nitrate causing it, we can see it doesn't affect thyroid function, which leaves realistically other variables like keith has stated. These are much more realistic and manageable.

Also, I wouldn't be surprised if organizations for animal rights are spreading the nonsense about fish needing a ton of space. I have seen people get banned off forums or yelled at for saying they would have more than 1 goldfish in a 10 gallon tank (AP or not). Yes, from so called experts on online communities as well... I digress..

As to date from the research we have all been able to pool and review we know that nitrate toxicity in fish is rare, but in special cases of specific species and specific to stages of life cycles there may be low to medium levels of nitrate toxicity (and in extremely rare situations high). Catfish seem pretty tolerant and Tilapia probably require a well placed nuke to take them out. Those are probably the 2 most commonly grown fish in AP.

[badflash]

For tilapia 200 ppm nitrate is safe with 300 ppm being the lower toxic limit. See
https://srac.tamu.edu/index.cfm/event/g ... tsheet/52/ (https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/52/)

[wh33t]

Wow guys, I'm upset that the forums never emailed to let me know there was a reply to this. Thank you very much for responses.

I was considering switching to Talapia early on, but I went to the store and bought a frozen talapia and cooked it up, it tasted like a muddy lake bottom, which is what everyone told me it would taste like. I considered that in a pond/res with no muddy lake bottom they might not have that taste, but everyone I know basically told me I could never expect the clarity of taste that would compare with a natural lake and certainly not the ocean. So I went to gold fish and decided to plan not to eat the fish.

What do you guys think about that?

I was considering growing some Talapia to use as Cat food for my cat. He's pretty old and pretty picky about his food and I'd love to feed him high quality proteins and fats during his last years.

[davidstcldfl]

Hi wh33t, 'I think' you only recieve an email, 'if' someone sends you a 'PM".

As far as a muddy taste, some folks purge them for a few days.
I've caught tilapia out of my aquaopnics system and ate them. (without purging) and they taste fine.

[urbanfarmer]

Any fish can have that muddy flavor. It has to do with the environment it is in. As David said you can purge the fish for a few days or so and the taste will be diminished or gone. That's assuming your fish will even have the muddy flavor.

[wh33t]

Well alright then. I'll try some Talapia ;)

[urbanfarmer]

Let us know how it goes! :D

[rfeiller]

If you use the full editor and click on notify me when a reply is posted you will be emailed

[davidstcldfl]

If you use the full editor and click on notify me when a reply is posted you will be emailed

Good eye rfeiller... :D

[Bioritize]

Not to highjack a thread but what are the safe levels of Nitrite?

About how long will it take a system to begin to cycle these?

[urbanfarmer]

Please see badflash's link to the "Tank Culture of Tilapia" published my SRAC. You can't go wrong with that as your guide.

This information is straight from the publication; although, I cannot agree the stated nitrate concentration figures as toxic based on my research and experience. There are ample publications and research that state nitrate is non-toxic to Tilapia. BUT, as the saying goes: it's better to be safe than sorry!


Nitrite (NO2-) — Avoid concentrations greater than 5 mg/L nitrite-nitrogen.

Nitrate (NO3-) — Nitrate toxicity can occur if levels in water reuse systems exceed the 300 to 400 mg/L nitrate-nitrogen range.

Just one more thing. Our "nitrate debate" is primarily academic. In aquaponic systems the nitrate concentration is often very low (double digits low or lower). It's pretty hard to get it even passed a few hundred (unless your system design is poor). Plants uptake nitrogen readily, and it is in fact a nutrient that controls/influences the uptake of other nutrients. The more nitrogen the more you need of everything else in proportion, and the plant will take up as much nitrogen as it can without remorse. It's like crack to a crack addict (or aquaponics to us). :lol: In other words, you really shouldn't see the nitrate high enough to harm the fish, period. (we're talking mature system not a new system trying to be cycled, but don't worry about nitrate toxicity in a new system in my opinion)

[wh33t]

If you use the full editor and click on notify me when a reply is posted you will be emailed

I have that set by default.

[Edward Blizz]

Nitrate, nitrate, and ammonia levels are all dependent on your aquaponics goals. Any increase of pollutant levels up from zero ppm is added stress for fish. Stressed fish are not happy fish. I don't want to eat unhappy fish.

If you are eating your fish or selling them for food, the water should be as clean as possible. If you are only into the fish part for the veggie benefits the levels can be much higher.

[bsfman]

Any increase of pollutant levels up from zero ppm is added stress for fish. Stressed fish are not happy fish. I don't want to eat unhappy fish.


Gee, I dunno Edward. My tilapia were wild caught - captured from a farm pond where they were prey for racoons, otters, eagles, ospreys, herons, egrets, seagulls, pelicans, gators, and big toothy spotted gar. They dealt with near lethal cool water temperatures in the winter, dramatic temperature fluctuations in the summer, near suffocation when the pond dried to a virtual puddle and dissolved oxygen levels plummeted during dry, hot weather and dramatic pH and chemical fluctuations when rain washed mud and organic matter into their environment.

Now, they live in a temperature controlled environment with zero ammonia and nitrites, plenty of dissolved oxygen, no predators to worry about, and all the food they can possibly want to eat. They are even able to have sex whenever and with whatever other amenable fish partner they choose.

Yes, perhaps their dissolved nitrates are higher than in that farm pond they came from (but perhaps not too! - No ag chems, or cow poop and cow urine to deal with now). Regardless, they are a lot less "stressed" than living in their wild environment. They nearly jump for joy when I lean over the tank to observe them or feed them. They seem pretty freakin' happy to me! When their time comes, I'll happily consume them! :)

[davidstcldfl]

Hi Edward...welcome to the forum... :D



They nearly jump for joy when I lean over the tank to observe them or feed them. They seem pretty freakin' happy to me!
:lol: :lol: :lol: They sound happy to me too.