Water Changes...Unnecessary?

[esoxlucius]

I like it when the big guns come out flexing their muscles, it just shows you how complex our hobby can be. For the rest of us mere mortals who just understand the basics, as hendre pointed out, just do your water changes, the rest will look after itself. I think there's a whopping big clue in the general name of the type of fish we keep that gives you an idea of the kind of environment we should keep our fish in.....that is "freshwater fish". I've never seen our wet pets referred to as "putridwater fish" or "toxicwater fish".

Do your water changes, keep that water "fresh".

 

[RD.]

7.6 mg/L NO3-N is 33.6 mg/L NO3-. That's pretty close to the 40 ppm Internet limit and that's with the most vulnerable life stage of one of the most sensitive species.

There's a huge increase in nitrate tolerance from eggs/fry to fingerlings. This appears to be true in every species studied. Rainbow trout appear to be one of the most sensitive yet fingerlings have 96 hr LC50 of 1310 mg/L NO3-N. Unless aquarium species are even more sensitive than salmonids, they'll be able to tolerate as much but very likely much more nitrate.

Yes, all true, except you missed the mark with your nitrate reading. Let's try this again, and perhaps at the same time Cory can explain how these researchers were reading elevated levels of nitrite or ammonia, as well.

The reports stated, 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.

That's not 33.6 mg/l N03, that's 4.8 - 33.6 mg/l N03.

4.8 ppm nitrate, and fish fry are adversely affected.

For this discussions purposes, I don't care what the species are, it proves that even at extremely low values, nitrates can negatively affect the health of a fish. That ought to be big enough clue for anyone with a lick of common sense, that we shouldn't simply ignore the potential toxic affects nitrate can have on at least some species of fish, during at least some of their life stages.

 

[J. H.]

WC are not all about nitrate. Evap and topoff can play havoc with dissolved salts, and with some fish, hormone buildup can be nearly as bad. Aquaponics people, who use plants to maintain 0 nitrate still (mostly) do occasional WC unless they are topping off with RO or rainwater. Some fish are tough, I've heard of goldfish being bred and fry being grown out in 50ppm water (can't seem to find the thread on the goldfish forum right now.), but I doubt you could keep a discus or a ram alive in water like that for a week. It all comes down to what you want to do - someone on here (I think thebiggerthebetter ) got a Giant Gourami that had been for years in a tank so small that it could not turn around, and it grew with its back curved because it couldn't straighten out, and not only did it live, but when it was put in a large tank, it learned how to swim again. There are also people on here who won't keep a JD in less than a 120 because they feel it's cramped. It's up to you to decide what you want to do, but IMO at some point it is cruelty to keep the fish.

 

[squint]

https://cpb-us-e1.wpmucdn.com/blogs...05/Water-Quality-Parameters-Sean-McGlynn1.pdf

"Nitrate-nitrogen levels below 90 mg/L and nitrite levels below 0.5 mg/L seem to have no effect on warm-water fish*, but salmon and other cold-water fish are more sensitive. The recommended nitrite minimum for salmon is 0.06 mg/L."

 

[squint]

For this discussions purposes, I don't care what the species are, it proves that even at extremely low values, nitrates can negatively affect the health of a fish. That ought to be big enough clue for anyone with a lick of common sense, that we shouldn't simply ignore the potential toxic affects nitrate can have on at least some species of fish, during at least some of their life stages.

Weren't you saying earlier that nitrate sensitivity varies with species and life stage? But now it's not important. We can extrapolate from one life stage and one species to a variety tropical fish species.

I never said eggs and fry of some species weren't sensitive. I've repeatedly pointed out that once they mature past those stages their nitrate tolerance skyrockets. In the example of rainbow trout, it increases to around 6,000 mg/L NO3-.

Does anybody here have salmon or trout fry in their tanks at home?

P.S. I think you mean "toxic effects."

 

[RD.]

Lol, where did I say that it's not important? I agree, we can extrapolate from one life stage and one species to a variety tropical fish species, but with so many unknowns in ornamental species it seems a bit ludicrous to me to extrapolate the little data available, to ALL species. Many members here do in fact breed fish, and raise eggs/larvae/fry. Is nitrate the be all to end all, of course not, but to totally dismiss it seems to fly in the face of what we currently know.

And these studies that you keep citing, contain but a small select sampling of ornamental species (how many MFKer's keep guppies?), many contain none.

Either way, as I originally stated, for the average hobbyist, nitrate levels are still a good overall gauge as to the overall condition of their tank water.

 

[Viridis]

https://cpb-us-e1.wpmucdn.com/blogs...05/Water-Quality-Parameters-Sean-McGlynn1.pdf

"Nitrate-nitrogen levels below 90 mg/L and nitrite levels below 0.5 mg/L seem to have no effect on warm-water fish*, but salmon and other cold-water fish are more sensitive. The recommended nitrite minimum for salmon is 0.06 mg/L."

What's the asterisk/footnote? Is there an exception?

 

[squint]

What's the asterisk/footnote? Is there an exception?

None that I could see.

 

[Coryloach]

Acute and Chronic Toxicity of Nitrate to Early Life Stages of Zebrafish—Setting Nitrate Safety Levels for Zebrafish Rearing
https://www.liebertpub.com/doi/abs/10.1089/zeb.2015.1098

The present study aimed to define nitrate safety levels for zebrafish based on acute and chronic toxicity bioassays in early life stages of this species. Acute bioassays revealed ontogenetic changes in response to high nitrate levels. Based on NOEC (no observed effect concentration) values, safety levels should be set at 1450, 1855, and 1075 mg/L NO3−-N to prevent acute lethal effects in embryos, newly-hatched larvae, and swim-up larvae, respectively. In the chronic bioassay, larvae were exposed to nitrate concentrations of 50, 100, 200, and 400 mg/L NO3−-N during the entire larval period (23 days). No negative effects were observed either on larval performance or condition at concentrations up to 200 mg/L NO3−-N. However, at 400 mg/L NO3−-N, survival drastically decreased and fish showed reduced growth and evidence of morphological abnormalities. Accordingly, a safety level of 200 mg/L NO3−-N is recommended during the larval rearing of zebrafish to prevent negative impacts on juvenile production.



Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates
https://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_2/2008/ref2426.pdf

Trama (1954) found that the common bluegill Lepomis macrochirus was able to tolerate elevated nitrate levels during short-term exposures: a 96 h LC50 value of 1975 mg NO3-N/l was estimated for this fish species (Table 3). Dowden and Bennett (1965) reported that the 24 h LC50 values of NaNO3 and KNO3 for L. macrochirus were 2110 and 761 mg NO3-N/l

Knepp and Arkin (1973) reported that the channel catfish Ictalurus punctatus was able to tolerate a nitrate concentration of 90 mg NO3-N/l without affecting their growth and feeding activity after an exposure of 164 days

Colt and Tchobanoglous (1976), evaluating the short-term toxicity of NaNO3 to fingerlings (50– 76 mm total length) of I. punctatus at 22, 26 and 30 C, calculated 96 h LC50 values of 1355, 1423 and 1400 mg NO3-N/l (Table 3). They concluded that the acute toxicity of nitrate to I. punctatus was independent of water temperature.

Westin (1974) reported that the 96 h LC50 values of nitrate for the rainbow trout Oncorhynchus mykiss (Salmo gairdneri, previously) and the chinook salmon Oncorhynchus tshawytscha were 1355 and 1310 mg NO3-N/l

Rubin and Elmaraghy (1977), after examining the acute toxicity of KNO3 to guppy (Poecilia reticulatus) fry, calculated 24, 48, 72 and 96 h LC50 values of 267, 219, 199 and 191 mg NO3-N/l

Tomasso and Carmichael (1986) reported that the 96 h LC50 value of nitrate for the Guadalupe bass Micropterus treculi was 1261 mg NO3-N/l

Tilak et al. (2002), using static and continuous flow through systems, determined 24 h LC50 values of 1565 and 1484 mg NO3-N/l for the Indian major carp Catla catla

Scott and Crunkilton (2000), after conducting laboratory experiments to examine the acute toxicity of NaNO3 to larvae (<8 day old) of the fathead minnow Pimephales promelas, found that the 96 h LC50 value fell within the range of 1010–1607 mg NO3-N/l (average LC50 value of 1341 mg NO3-N/l;

Scott and Crunkilton (2000) also reported that the noobserved-effect concentration (NOEC) and the lowestobserved-effect concentration (LOEC), for the growth of newly hatched larvae (<24 h old) of P. promelas after an exposure of 7 days, were 358 and 717 mg NO3-N/l

The first indication that relatively low concentrations of nitrate might be harmful to fish came from Grabda et al. (1974). They reported that fry of rainbow trout, exposed to 5–6 mg NO3-N/l for several days, displayed increased blood levels of ferrihemoglobin, alterations in the peripheral blood and hematopoietic centres, and liver damage. In addition, Kincheloe et al. (1979), examining the tolerance of several salmonid species to nitrate toxicity after an exposure of 30 days, reported that developing eggs and early fry stages of O. mykiss, O. tshawytscha and the (Lahontan) cutthroat trout Salmo clarki exhibited significant increases in mortality at nitrate concentrations from 1.1 to 4.5 mg NO3-N/l (Table 3). In the case of the coho salmon Oncorhynchus kisutch, eggs and fry were not affected at the highest nitrate concentration of 4.5 mg NO3-N/l (Table 3). Kincheloe et al. (1979) concluded that a nitrate level as low as 2.0 mg NO3- N/l in surface waters of low total hardness (<40 mg CaCO3/l) would be expected to limit survival of some salmonid fish populations because of impaired reproductive success.

 

[Coryloach]

In this study the tested nitrate levels of 100 mg/L NO3-N were found to have no effect to the well being of the fish, however, there is an interesting paragraph on elevated nitrite nitrogen when nitrate is higher referencing several studies.

Evaluating the chronic effects of nitrate on the health and performance of post-smolt Atlantic salmon Salmo salar in freshwater recirculation aquaculture systems

https://www.sciencedirect.com/science/article/pii/S0144860917301231

The authors found it impossible, however, to control every water quality variable among treatments, and a few parameters other than nitrate-nitrogen were significantly different, including boron, calcium, carbon dioxide, nitrite-nitrogen, potassium, sodium, sulfate, dissolved sulfur, true color, and ultraviolet transmittance (Tables 5 and 6). In the case of most of these parameters, the magnitude of difference between treatments was relatively low and the concentrations/levels were diluted. High water flushing rates were intentionally established to maintain water quality concentrations other than nitrate at low levels and thereby focus on the effect of nitrate alone. Davidson et al. (2014)also noted significantly different levels of boron, calcium, nitrite-nitrogen, potassium, sodium, sulfate, sulfur, and ultraviolet transmittance related to treatments when evaluating the effects of NO3-N concentrations on rainbow trout health and performance. The reoccurrence of these differences indicates that sodium nitrate and sodium sulfate dosing influence these water quality parameters. Davidson et al. (2014) also suggested that elevated nitrite-nitrogen was related to back conversion of available nitrate through passive denitrification. A correlation between sodium nitrate dosing and increased nitrite was also reported by Freitag et al. (2015) during a study evaluating the effects of nitrate on Atlantic salmon endocrine function.