Hobby test kits are not accurate, and nitrates are not as harmful as many people believe.
Hobby NO3 test kits are not accurate, and nitrates are not as harmful as many people believe.
"Ammonia and nitrite are both toxic to fishes. Ammonia toxicity is thought to occur from
osmoregulatory imbalance causing renal failure and gill epithelial damage resulting in suffocation,
decreased excretion of endogenous ammonia, and general neurological and cytological failure
(Meade, 1985). Elevated nitrite levels cause methemoglobinemia (brown blood disease). Nitrate is
generally considered nontoxic to fishes (Bromage et al. 1988). In most aquaculture systems, nitrate
levels are below 50 mg/L, but in intensive culture systems, nitrate levels often exceed 100 mg/L.
Nitrate levels, in recirculating systems that have limited fresh water input, can be 200 mg/L or greater" - Nitrate Toxicity: A Potential Problem of Recirculating Systems, Terry C. Hrubec https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.455.5315&rep=rep1&type=pdf#page=31
"Only a recommended standard, rather than a mandatory one has been set by the U.S. Environmental Protection Agency (EPA) since nitrate has long been considered to be almost nontoxic to fish (EPA 1976). For example, WESTIN (1974) reported a 96-h TLm of 5,800 ppm nitrate to chinook salmon fingerlings (Oncorhynchus tshawytscha) and 6,000 ppm for rainbow trout fingerlings (Salmo gairdneri). " - Tolerance of Developing Salmonid Eggs and Fry to Nitrate
Exposure , John W. Kincheloe et. al., Bull. Environm. Contain. Toxicol. 23,575-578 (1979)
https://link.springer.com/article/10.1007%2FBF01770006
It has been observed that hobby grade nitrate test kits are not very accurate and can be at times plus or minus 100% in accuracy.
Lab grade kits are accurate - but they're five times the price. LaMotte and Hach are ones found in a lab.
Note also the LC50 (point at which half the test animals die) for nitrAte varies but if usually over 1000 ppm for freshwater fish and several times that for marine fish. Nitrate is just not that harmful; plant enthusiasts add nitrate on the order of 30-50 ppm with no ill effects all the time.
One time while making up fertilizer I accidentally slipped a digit making fertilizer and kept one tank at 300 ppm for a month that had plants, sensitive rainwater killifish (Diapteron), snails as well as shrimp. Not one of these showed any signs of distress; the tips of Cryptocoryne and Echinodorus tend to curl a little bit.
Worry about ammonia. It can be fatal in concentrations too low to register or on hobby test kits and is the one that kills. NitrItes are harmful but are so at much much higher levels than ammonia is.
I haven't bothered with test kits in ages. Analogous to the maxim "if you own a grocery store and have to smell the produce to see if it's fresh, then throw it out" my take on this has been "if you think you need to test the water, change all of it".
I can see spending the money on a lab grade ammonia test kit but really question why people waste money on nitrate tests.
This also explains why some poeple report 20-30 ppm NO3 from the tap when the water company says < 5 ppm. Beware of old test hobby test kits and it may be a good idea to compare tap water to the values the water company has as a rough form of calibration.
References:
Nitrates
LD50 (Lethal Dose 50%) has been a common dose estimate for acute toxicity. It is a statistically derived maximum dose at which 50% of the group of organisms (rat, mouse, or other species) would be expected to die. Lethal Concentration 50% (LC50) — for inhalation toxicity, air concentrations are used for exposure values. The LC50 refers to the calculated concentration of a gas lethal to 50% of a group. Occasionally LC0 and LC10 are also used. Toxic Doses (TDs) are used to indicate doses that cause adverse toxic effects. The usual dose estimates include: TD0, TD10, TD50 and TD90.
Dose Estimates of Toxic Effects https://toxtutor.nlm.nih.gov/02-004.html
LC50: 1078ppm - 397ppm in Sturgeon varying in size an age. Older larger fish were most susceptible
Nitrate toxicity in Siberian sturgeon (Acipenser baeri), H.J.Hamlin; Aquaculture, Volume 253, Issues 1–4, 31 March 2006, Pages 688-693
https://www.sciencedirect.com/science/article/abs/pii/S0044848605005545
"Nitrate concentrations may actually exceed values as high as 25 ppm in surface waters and 100 ppm in ground waters (Bogardi et al., 1991; Goodrich et al., 1991; Gleick, 1993; Ministry of Agriculture, Fisheries and Food, 1993; Steinheimer et al., 1998). On the other hand, in marine aquaria and aquaculture systems, where water is recirculating with good oxygenation, nitrate concentrations can approach values of 500 ppm (De Graaf, 1964; Pierce et al., 1993)."
"In fact, although safe levels of ammonia have been well established for fishes and aquatic invertebrates (Alabaster and Lloyd, 1982; US Environmental Protection Agency, 1986), no safe level of nitrate has been established for aquatic animals
(US Environmental Protection Agency, 1986; Scott and Crunkilton, 2000)."
"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 NO3 uptake in aquatic animals seems to be more limited than the uptake of NH4 and NO2, 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)"
"In general, freshwater invertebrates appear to be more sensitive to nitrate toxicity than marine invertebrates as a probable
consequence of the ameliorating effect of water salinity on the tolerance of aquatic invertebrates to nitrate ions. However, early life stages of some marine invertebrates may be very sensitive to nitrate toxicity (Muir et al., 1991)."
"Meade and Watts (1995) examined the toxic effects of NaNO3 on the survival and metabolic rate (oxygen consumption) in juvenile individuals (9–13 mm total length) of the Australian freshwater crayfish Cherax quadricarinatus. After 5 days, no mortality was observed in crayfish exposed to a nominal nitrate concentration of 1000 ppm. Furthermore, no significant difference was observed in oxygen consumption between control (0 ppm) and experimental (1000 ppm) individuals (Table 1)"
"Scott and Crunkilton (2000), examining the acute toxicity of NaNO3 to neonates of the cladocerans Ceriodaphnia dubia (<24 h old) and Daphnia magna (<48 h old), estimated 48 h LC50 values of 374 and 462 ppm"
Guppy (Poecilia reticulata) 24, 48, 72 and 96 h LC50 values of 267, 219, 199 and 191 ppm
Fathead minnow (Pimephales promelas) found that the 96 h LC50 value fell within the range of 1010–1607 ppm
Guadalupe bass (Micropterus treculi) 1261 ppm
Lepomis macrochirus 96 h LC50 value of 1975 ppm (Trama 1954)
24 h LC50 values of NaNO3 and KNO3 for L. macrochirus were 2110 and 761 ppm (Dowden and Bennett 1965) Oncorhynchus mykiss 1355 and 1310 ppm Ictalurus punctatus 1355 - 1433 ppm Catla catla 1565 and 1484 ppm Heteromycteris capensis 5050 ppm Diplodus saegus 3650 ppm
Indian major carp Catla catla 24 h LC50 values of 1565 and 1484 ppm
These sticklebacks survived concentrations of 500 ppm sodium nitrate and 800 ppm calcium nitrate for 10 days.
Trama [13] found the relative toxicity of the anions to be chloride less than nitrate, which was less than sulfate. He reported the 96-hour median tolerance limit (TLm) for bluegills at 20 C to be 12,000 ppm sodium nitrate and 3,000 ppm potassium nitrate.
"This then would give a maximum allowable concentration for chinooks of 370 ppm NO3 and 250 ppm for trout. But best results
of growth and good health, based on observations of chinooks in recirculating filter systems with varying nitrate concentrations and fish health, would not exceed 1/100 of this LC10 concentration, or 25 to 35 ppm. This is 10 to 20 ppm less than the recommended limit for farmstead uses as reported by the National Technical Advisory Committee [7]. Following this reasoning, a maximum allowable level for nitrate in freshwater (1/10 of 10-day LC10) would be 0.12 ppm NO.,. Since nitrite is known to be much more toxic to most animals, the 1/100 factor (0.012 ppm NO._,), which is less than Klinger's 0.03 ppm detectable level, is probably safer still. Once the mode of action of nitrate as a toxicant can be defined more clearly, probably through measurements of blood nitrate and nitrite levels, and the sublethal effects of nitrate and nitrite to fish can be established, these application factors will become more solidly defined."
Westin, D. T. (1974). Nitrate and Nitrite Toxicity to Salmonoid Fishes. The Progressive Fish-Culturist, 36(2), 86–89. doi:10.1577/1548-8659(1974)36[86:nantts]2.0.co;2
https://www.tandfonline.com/doi/abs/10.1577/1548-8659%281974%2936%5B86%3ANANTTS%5D2.0.CO%3B2
Nitrites
The most common non-infectious problem may be high nitrite levels caused by biofilter malfunction
(Durant, FI and Hinshaw, North Carolina State University, personal communication). Nitrite toxicity
is pH-dependent and dependent, in varying degrees, on the presence of chloride, sulfate, phosphate,
and nitrate ions in the water (Russo et al. 1981). Wedemeyer and Yasutake (1978) reported a
reduction in nitrite toxicity as pH increased. Russo and Thurston (1977) reported that the presence
of chloride ion suppressed nitrite toxicity in rainbow trout and Bowser et al. (1989) found chloride
to have a protective effect against nitrite toxicity in Atlantic salmon (Salmo salar). Sodium chloride
is used to control nitrite toxicity in fish culture systems as the chloride ion is taken up by the gills
preferentially to nitrite ion (Perrone and Meade 1977).
The 96-h LC50 value of nitrite to rainbow trout is 0.20 to 0.40 mg/L as N02-N (Russo and Thurston,
1977). However, the toxicity depends upon the concentration of calcium or chloride ions, which can
increase the tolerance of rainbow trout to nitrite by a factor of 20 to 30 times (Colt and Armstrong,
1981). The desirable level of nitrite for trout culture in a reuse system is <0.1 mg/L (Hankins, Fl,
personal communication).
At the FI, the biofilter was broken-in naturally by stocking the tanks at low density and allowing the
ammonia produced by the fish to increase the nitrifying bacteria population. Nitrobacter multiply
more slowly at the lower water temperatures (Kaiser and Wheaton 1983) found in the FI system (e.g.,
15EC), so there was a lag period when nitrites accumulated. Once the biofilter reached a steady state
the problem disappeared. At the FI palliative measures were taken when nitrite reached a level of 0.3
mg/L. Salt was added directly to the culture tanks at 10 times the nitrite concentration to reduce
toxicity. Abrupt increases in salinity may impair nitrification and biofilter recovery.
Major Diseases Encountered in Rainbow Trout Reared in Recirculating Systems
Alicia C. Noble
The Conservation Fund's Freshwater Institute
Shepherdstown, West Virginia
Klinger [3], reporting on the toxicity of sodium nitrite to minnows (Phoxinus laevia), observed that 50 mg/1 could be fatal in 14 days. He found that 10 mg/1 was the threshold concentration above which toxic effects ensue, and that 0.03 mg/1 was the minimum detectable level for these minnows. McCoy [6] reported on tests of NO.,-N levels found in lakes and stream systems to 13 species of fish. She found great differences in susceptibility of the fishes to NO.,-N levels. Logperch (Percina caprodes)
were the most sensitive of those species tested, dying in less than 3 hours at 5 ppm NOo.-N (16.5 ppm NO.,). By contrast, carp (Cyprinus carpio) and black bullheads (Ictalurus melas) survived 40 ppm NO•-N (132 ppm NO2) beyond the 48 hours of the test exposure.
https://www.tandfonline.com/doi/abs/10.1577/1548-8659%281974%2936%5B86%3ANANTTS%5D2.0.CO%3B2
Pike-perch Sander lucioperca is currently considered as one of the most promising candidates for production in freshwater recirculation aquaculture systems (RAS). Here, due to the lack of studies on nitrite (NO2−) toxicity in pike-perch, a flow-through exposure at 0, 0.44, 0.88, 1.75, 3.5, 7, 14 and 28 mg/L NO2−–N was carried out to determine the acute and chronic toxicity over a period of 32 days. In juvenile pike-perch, 120 h LC50 was 6.1 mg/L NO2−–N and at ≥ 14 mg/L NO2−–N all fish had died within 24 h. Chronic exposure revealed a significant build up of NO2− in the plasma as well as in the muscles at ≥ 0.44 mg/L NO2−–N peaking in fish exposed to the highest concentration of 3.5 mg/L NO2−–N after 32 days. Still, due to high individual variation methemoglobin (MetHb) was only significantly increased (p < 0.01) at 3.5 mg/L NO2−–N. No adverse effects on red blood cells (RBC) and hematocrit were observed in any of the treatments. In a second experiment, compensation of NO2− toxicity at increasing chloride concentrations (40 (freshwater), 65, 90, 140, 240, 440 mg/L Cl−) was observed at a constant exposure of 10 mg/L NO2−–N for 42 days. At ≥ 240 mg/L Cl−, NO2− build-up in blood plasma and muscle was completely inhibited. At lower Cl− concentrations (≤ 140 mg/L), NO2− was significantly increased in plasma, but only insignificantly elevated in muscle due to high individual variation. MetHb was increased significantly difference only at 40 mg/L Cl− (freshwater control) compared to the control. Again, high individual variations were observed. As a conclusion, S. lucioperca is moderately sensitive towards NO2− and acceptable levels in RAS should hence not exceed 1.75 mg/L NO2−–N to avoid MetHb formation. However, based on the 120 h LC50 and a factor of 0.01 according to Sprague (1971), a NO2− concentration of ≤ 0.061 mg/L NO2−–N is considered as “safe.” Thereby, no NO2− should accumulate in the plasma or muscle tissue during chronic exposure. For 10 mg/L NO2−–N, ≥ 240 mg/L chloride compensates for NO2− uptake in plasma and muscle.
Acute and chronic nitrite toxicity in juvenile pike-perch (Sander lucioperca) and its compensation by chloride
S.Wuertza, S.G.E.Schulze, U.Eberhardt, C.Schulz, J.P.Schroeder
Physiology Part C: Toxicology & Pharmacology Volume 157, Issue 4, May 2013, Pages 352-360 https://www.sciencedirect.com/science/article/abs/pii/S1532045613000033
