Hey y'all, I'm curious about the units when discussing safe Nitrate levels among aquarium enthusiasts. I've seen numbers like under 20, 30, 40, 100 ppm thrown out as safe levels. But none of these articles and forums specify if this is referring to nitrogen-nitrate (NO3-N) or just Nitrate (NO3) concentrations. Water testing labs report nitrate in NO3-N, the EPA guideline being 10 ppm NO3-N. But that is 44 ppm of NO3. So what are the units we're talking in the fish world? Maybe the better question is what do test kits use since I assume we're all talking the same language.
Nitrate Units
- Thread starter cmeier7
- Start date
NO3. Really depends on fish and other water parameters. But I think consensus is 20ppm or lower. Obviously lower is better. Most natural environments are 0 or near.
For a long time I accepted the claim of near zero nitrates in natural aquatic habitats, but after stumbling into an article contradicting this, and starting to search the scientific literature, I'm finding practically everywhere I look in the scientific literature that it's not true. It's like some other things we've heard so often we think it's true.
I'm finding there is a ton of technical literature on this-- surveys of nitrate, ammonium, and other forms of nitrogen in many South American rivers, tables comparing regions and river types, articles referencing nitrogen "cycling" in these habitats, etc. There are studies of nitrates and other nutrients deposited into the Atlantic by the Amazon, what then happens to each nutrient as various microbes metabolize them, etc. I'd provide reference links, but at this stage it's a new topic for me and I'm swamped finding and trying to digest the huge volume of information out there into something I'd post.
But as one example, I keep reading that Amazon forest rivers have more nitrates than pasture rivers, which have more phosphate, and that river habitats generally have more nitrates than lakes, studies of algae "uptake" of these nutrients, including nitrates, flowing into various lakes from river flooding, etc.
All of that said, experience in the hobby seems to have well established that lower nitrates are better for aquarium fish, but not everyone agrees on the numbers and some species are more sensitive than others-- and/or sensitive to whatever else happens chemically and organically in association with high vs. low nitrates.
I'm finding there is a ton of technical literature on this-- surveys of nitrate, ammonium, and other forms of nitrogen in many South American rivers, tables comparing regions and river types, articles referencing nitrogen "cycling" in these habitats, etc. There are studies of nitrates and other nutrients deposited into the Atlantic by the Amazon, what then happens to each nutrient as various microbes metabolize them, etc. I'd provide reference links, but at this stage it's a new topic for me and I'm swamped finding and trying to digest the huge volume of information out there into something I'd post.
But as one example, I keep reading that Amazon forest rivers have more nitrates than pasture rivers, which have more phosphate, and that river habitats generally have more nitrates than lakes, studies of algae "uptake" of these nutrients, including nitrates, flowing into various lakes from river flooding, etc.
All of that said, experience in the hobby seems to have well established that lower nitrates are better for aquarium fish, but not everyone agrees on the numbers and some species are more sensitive than others-- and/or sensitive to whatever else happens chemically and organically in association with high vs. low nitrates.
...All of that said, I try to keep my nitrates low and I often achieve 5 ppm in my tanks, but to be honest when I kept and bred Malawi cichlids, and fabulously overstocked those tanks, I didn't have any issues when my tanks ran a good bit higher than that-- but again, some species are more sensitive than others.
I don't fully understand the nitrate thing, and reading scientific papers doesn't change that, lol. So
neutrino
, when you get your head round it all be sure to post up a version we can all understand. 
The simple fact is we're told nitrate is bad (how bad???) and you need to keep it as low (how low???) as possible. Our go to method of nitrate testing is the API liquid test kit which states, rightly or wrongly, that "a nitrate level of 40ppm (mg/l) or less is recommended for freshwater aquariums". Because API state this I suspect that many hobbyists may plum for 40ppm as 'the target', without even understanding what 40ppm even means to our tank inhabitants.
Personally I never let my nitrate go any deeper in colour than an orange shade on water change day, so i'm in the 10-20ppm bracket. It very rarely goes anywhere near the red spectrum, and if it does i look into it, because it would mean i'd done something to cause that.
What throws me is that you hear or read these unsubstantiated stories of hobbyists breeding in aquariums which are very high in nitrate, I mean off the scale high.
neutrino
, when you get your head round it all be sure to post up a version we can all understand. The simple fact is we're told nitrate is bad (how bad???) and you need to keep it as low (how low???) as possible. Our go to method of nitrate testing is the API liquid test kit which states, rightly or wrongly, that "a nitrate level of 40ppm (mg/l) or less is recommended for freshwater aquariums". Because API state this I suspect that many hobbyists may plum for 40ppm as 'the target', without even understanding what 40ppm even means to our tank inhabitants.
Personally I never let my nitrate go any deeper in colour than an orange shade on water change day, so i'm in the 10-20ppm bracket. It very rarely goes anywhere near the red spectrum, and if it does i look into it, because it would mean i'd done something to cause that.
What throws me is that you hear or read these unsubstantiated stories of hobbyists breeding in aquariums which are very high in nitrate, I mean off the scale high.
Nitrate is a bacterial waste product.
As part of my job for over a decade as a chemist/water analyst, I measured water parameters of raw lake Michigan water.
Nitrate barely ever exceeded 1 ppm, and then only during seasonal lake turn over (never higher than 2ppm.
Nitrate averaged under 1 ppm, most of the year.
My testing procedures were using the same method as API, but using much accurate photospectrometers, and EPA required reagents, to read results that measured down to the hundredth place.
Here in Panama, I use the simple aquarium API kit, and in non-polluted areas.
All samples presented so far, have been 5ppm or below.
Samples taken in any polluted agricultural area, where heavy fertilization is used, are much higher.
I look at nitrate above 10ppm as a chronic causer of stress.
Probably not relevant for short lived fish species like cardinal tetras, of small live bearers, with normal life spans of 3 years or less.
But for species like oscars and other cichlids that easily live 10 or more years, chronic can be an issue.
Although it may not cause acute reactions, in fish with long lives, HLLE, and other diseases seem to be exacerbated by any higher nitrate concentrations, but usually not visually manifesting until they are adults.
Its effects are similar to diseases like lung cancer from smoking.
1 cigarette per day for 20 years, maybe no prob (akin to a constant nitrate concentration of 5ppm).
But a pack a day for 20 years, emphysema, and tumors in many (not all). (akin to a nitrate concentration of 20ppm or above)
Additional stress causes may also determine the outcome. i.e other water parameters outside that particular species norm (like a soft water species held in hard water), crowded conditions, over feeding the list goes on.
We only need to look at the disease section, where anecdotal evidence is rampant, where posts like "why is my oscar showing signs of hole in the head? I haven't done anything different".
and when asked to show water parameters, and nitrate is 20-40ppm or higher, along with 3 times per day feeding, and few, or same water change schedule as when the oscar, severum, P-bass or other large cichlid was 2 or 3"..
As part of my job for over a decade as a chemist/water analyst, I measured water parameters of raw lake Michigan water.
Nitrate barely ever exceeded 1 ppm, and then only during seasonal lake turn over (never higher than 2ppm.
Nitrate averaged under 1 ppm, most of the year.
My testing procedures were using the same method as API, but using much accurate photospectrometers, and EPA required reagents, to read results that measured down to the hundredth place.
Here in Panama, I use the simple aquarium API kit, and in non-polluted areas.
All samples presented so far, have been 5ppm or below.
Samples taken in any polluted agricultural area, where heavy fertilization is used, are much higher.
I look at nitrate above 10ppm as a chronic causer of stress.
Probably not relevant for short lived fish species like cardinal tetras, of small live bearers, with normal life spans of 3 years or less.
But for species like oscars and other cichlids that easily live 10 or more years, chronic can be an issue.
Although it may not cause acute reactions, in fish with long lives, HLLE, and other diseases seem to be exacerbated by any higher nitrate concentrations, but usually not visually manifesting until they are adults.
Its effects are similar to diseases like lung cancer from smoking.
1 cigarette per day for 20 years, maybe no prob (akin to a constant nitrate concentration of 5ppm).
But a pack a day for 20 years, emphysema, and tumors in many (not all). (akin to a nitrate concentration of 20ppm or above)
Additional stress causes may also determine the outcome. i.e other water parameters outside that particular species norm (like a soft water species held in hard water), crowded conditions, over feeding the list goes on.
We only need to look at the disease section, where anecdotal evidence is rampant, where posts like "why is my oscar showing signs of hole in the head? I haven't done anything different".
and when asked to show water parameters, and nitrate is 20-40ppm or higher, along with 3 times per day feeding, and few, or same water change schedule as when the oscar, severum, P-bass or other large cichlid was 2 or 3"..
Thanks everyone for the commentary. I also checked with API and the confirm the testing kits provide results in NO3 ions. Not good news that we're talking in NO3 and not NO3-N. I'm moving to a rural acreage in an agricultural zone, and the well water tests at 11ppm NO3-N which is just shy of 50ppm NO3! I know of options to reduce nitrate such as RO filtration, specialized anaerobic bacteria filter medias, having a planted bog filter, etc. But I don't know yet what option might be best and I'm not too happy about potentially needing to spend a lot more money just to condition the water for my fish. I have a large aquarium with Amazon river fish, we're talking 40-50 gallons to do a 20% water change. I suppose this is all a discussion for anther forum.
Fish are also quite adaptive. Whilst keeping nitrates as low as possible is always good, some species are more able to accept higher nitrates than others, with little or no detrimental signs or shortened lifespan.
I personally have a soft coral reef setup which is now eight years old with tangs and clowns that are there from the get go which is continuously over 40ppm. The coral and fish are thriving and the clowns breed regularly. I use RO water but know I tend to over feed. That said, when I tried to reduce the nitrate level gradually I experienced die back of coral which in turn started to impact the fish.
Yes this is marine, but same can be applied to fresh IMO.
I don’t suggest keeping fish in “dirty” water, and I do suggest keeping a regular water change regime , however some of us just have to live with the fact that water comes out of the tap at 40ppm and do the best we can with that. Including spending many years breeding countless species in water 40ppm and above.
I personally have a soft coral reef setup which is now eight years old with tangs and clowns that are there from the get go which is continuously over 40ppm. The coral and fish are thriving and the clowns breed regularly. I use RO water but know I tend to over feed. That said, when I tried to reduce the nitrate level gradually I experienced die back of coral which in turn started to impact the fish.
Yes this is marine, but same can be applied to fresh IMO.
I don’t suggest keeping fish in “dirty” water, and I do suggest keeping a regular water change regime , however some of us just have to live with the fact that water comes out of the tap at 40ppm and do the best we can with that. Including spending many years breeding countless species in water 40ppm and above.