Water Changes...Unnecessary?

[RD.]

If there's only ever been one long-term nitrate toxicity study involving fish, and it only involved two species of fish, how can you possibly claim that nitrate is essentially non-toxic to adult fish?

And determining a tolerance level, is a FAR cry from stating that excessively high levels of nitrates will cause no negative health issues with all species of fin fish, at any/all stages of growth. This particular paper is based simply on "observations", without performing a necropsy on any of the subjects at the end of their 164 day trial? Are you plucking kidding me?


I am a great believer in science, but many studies start out with a preconceived notion, and the "study" ends where the researcher/s involved can say, there, told ya so. All that research proved, was in those two species of fish, neither growth nor feeding activity were significantly affected in a negative manner, within a 164 day timeframe. Nothing more, nothing less.

 

[squint]

There are numerous studies on nitrate toxicity. The common theme is that it takes thousands of mg/L nitrate to kill adult fish.

I looked at the research and concluded nitrate isn't toxic.

Tom Barr looked at the research and concluded nitrate isn't toxic.

Diana Walstad looked at the research and concluded nitrate isn't toxic.

John Kuhns also says nitrate isn't toxic.

Remember, these values have to be multiplied by 4.43 to be converted to API units. Also, this review doesn't even include the newer studies that also found nitrate to be non-toxic.

 

[Stephen St.Clair]

My head hurts, too much mathematical info. Lol.
For what it's worth, general observations; directly after my weekly 50% WC of the display tank, I notice marked positive behavior and color changes in the fish.
The fish virtually attack food at feedings; schooling and playful chasing increase and the fish display more vivid colors. By midweek things slow down a bit, likely due to the slow deterioration of the water quality.

 

[RD.]

LOL, squint you are the one that stated; "There's really only ever been one long-term nitrate toxicity study".

And to state that nitrate isn't toxic, is a far cry from stating that over long term periods, excessive nitrate has zero negative health affects on ALL species of fish. Your chart shows a mere drop in the bucket as far as species kept in aquariums by hobbyists. In fact most studies involving fish, involve fish grown and sold for commercial purposes. Who cares what a fingerling rainbow trout can tolerate? I mean nice to know, but certainly doesn't mean that one can necessarily extrapolate that data, to say the same would hold true with some wild synodontis collected in Lake Tanganyika.

And quite frankly I don't care what Tom Barr, Diana Walstad or John Kuhns concluded. lol It's not like any of them wrote the bible on finfish toxins, and/or at what levels all various substances found in an aquarium become toxic.

Seeing as you enjoy science, take a read on what a real expert in the health of finfish, Edward J. Noga, has to say on this subject.

edited due to copyright issues.....

 

[RD.]

For those that don't own Edward J Noga's book, just google for a bit. His take is certainly different from what squint has been presenting here.

Here's a short cut, read carefully .......

https://books.google.ca/books?id=M5GZGH3W-IEC&pg=PT128&lpg=PT128&dq=edward+noga+nitrate+toxicity&source=bl&ots=jb52YK67V9&sig=W3H7uBGtOn2gqPMBiPHi5c_Uego&hl=en&sa=X&ved=0ahUKEwikq47BhszaAhUXwGMKHWISCigQ6AEILDAB#v=onepage&q=edward noga nitrate toxicity&f=false

 

[squint]

I don't see anything published by Noga on fish toxicity. Most of his publications are about fish disease.

In his book on fish disease, he references several of the same papers I do (Camargo and Kincheloe) but no research of his own (because he hasn't done any research on the subject).

He does talk about cultured fish a lot, like rainbow and cutthroat trout. I thought you said we should ignore those? He mentions bluegill as well.

So, we have science on one side and the Internet on the other side. I'm going to go with science.

Edit: Here's a quote from Noga's book: "Most fish species tolerate very high levels; toxic levels for bluegills, guppies, and channel catfish range from 200 to 2,000 mg NO3-N/l." That's a whopping 885-8850 mg/L in API units!

 

[duanes]

I have read the Noga studies, and although he states in many, nitrate may not be acutely toxic to adult fish, he does suggest that high nitrate (in tandem) with other stress related factors contribute to chronic problems in aquarium fish. We've all seen old scarred up oscars, way too often.
Overcrowding, small tanks, overfeeding, lack of tannins, lack of attention to a certain species natural conditions (one size (temp, pH, conductivity) doesn't fit all) etc etc.) A few generations in a tank, does not negate millions of years of evolution,
I also agree that nitrate is "not" the sole reason for water changes, pheromones, other mineral buildup, and diluting pathogenic bacterial populations are all reason enough to lose old water, whether nitrate is high or not.
And since freshwater fish are constantly urinating from their gills, just diluting the urine soup of a tank, should (in my book) be enough to justify frequent water changes.

 

[Coryloach]

The nitrate debate is never ending.....

The problem with nitrate studies are that high nitrate levels are always coming hand in hand with elevated nitrite levels. This is due to naturally occurring denitrification when nitrates are elevated. So the "toxicity of nitrate"(NO3) is quite likely to be a nitrite (NO2) related. And we all know how toxic nitrite(NO2) is...If you read every comprehensive study carefully(not just some summed up results), you get these....

Examples:

"Fish exposed to the sodium nitrate and potassium nitrate began to die after six weeks at the elevated nitrate levels (200ppm)

With the exception of nitrate concentrations purposefully outside these ranges, our water quality was within the proposed
ranges for all water quality parameters except for nitrite. When nitrate levels were elevated due to
addition of a nitrate salt or from nitrification, increased nitrite levels were observed. This increase
in nitrite was most likely due to enhanced reduction of nitrate to nitrite caused by the elevated nitrate concentrations"

Nitrate Toxicity: A Potential Problem of... (PDF Download Available). Available from: https://www.researchgate.net/public..._A_Potential_Problem_of_Recirculating_Systems [accessed Apr 11 2018].



Another study:

Comparing the effects of high vs. low nitrate on the health, performance, and welfare of juvenile rainbow trout Oncorhynchus mykiss within water recirculating aquaculture systems
https://www.sciencedirect.com/science/article/pii/S0144860914000041#tbl0020


After reporting all the "toxicity" levels and effect of nitrate in their two study groups of low and high level nitrates, they also say the following somewhere down the bottom....

Several other water quality parameters were significantly different between treatments(e.g. low and high nitrate groups) These parameters included nitrite nitrogen......Nitrite nitrogen, total suspended solids, boron, and potassium concentrations were significantly greater within the high NO3-N treatment.


Apart from that, the toxicity levels of nitrate reported in majority of studies are measured in nitrate nirogen, meaning you've got to multiply that figure by 4 to get what we measure in tanks. The toxicity levels reported in majority of studies are in the several hundreds and thousands. Who has a tank with 400ppm nitrate?

In the below study for example the actual harmful levels of nitrate reported, when converted, are 440ppm nitrates and let's not forget the 160ppm sodium that comes along with the dosage of sodium nitrate.....

Nitrate and nitrite exposure affect cognitive behavior and oxygen consumption during exercise in zebrafish
https://www.fasebj.org/doi/abs/10.1096/fasebj.31.1_supplement.lb277


Additionally to the above, hypoxia due to excessive nitrification will occur first in highly polluted tanks before the fish get their chance at high nitrate levels....and subsequent denitrification. The tank will be oxygen deprived. The entire tank will be dead overnight. Go blame it on high nitrates...

 

[RD.]

Did you even bother to read what I linked to, squint? You are doing exactly what I stated up front regarding many researchers, they only see, and attempt to prove, what suits their needs/wants.

Dr. Edward J. Noga, MS, DVM, a highly respected professor of aquatic medicine and immunology, that has been published approx 150 times in related papers/journals. His lab at NC State University specializes in the study of infectious diseases of finfish and shellfish.

I first posted that blurb above, several yrs ago.

Getting back what he has published in his book, a book that many DVM's and commercial breeders consider the "bible" of fish disease, he also said ...

That almost no studies have examined the clinical effects of nitrate on fish (except mortality rate) but effects appear to reflect damage to hemoglobin.

He also states that fish vary greatly in susceptibility to nitrate poisoning and effects are probably much more subtle.

He goes on to state, that eggs and fry of both rainbow trout and cutthroat trout fry are adversely affected, and in some cases can die, after exposure for 30 days to as little as 1.1-7.6 mg N03 - N/L. How many whopping units is that in your API test kit?

He also explains the difference between acute toxicity, and chronic, and how nitrate is more of a chronic problem.

 

[squint]

Another quote from Noga's book: "While this is not feasible in ponds, nitrate does not appear to reach toxic levels under typical pond aquaculture situations. For example, exposure of channel catfish to 90 mg NO3−- nitrogen/l for nearly 6 months does not affect their health or growth (Camargo et al. 2005 )." Holy cow, he's referencing the same studies I am. I thought you said we should disregard studies on channel catfish yet here's Noga referencing them!