Maximum Safe Nitrate levels for fish?

[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!

[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/

[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!

[rfeiller]

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