Acceptable Nitrate Levels.

[Phreaker]

So I have seen the general advice here to always be 'keep nitrates under 20ppm'.
Why? What is this number based on?

Out test kits show nitrates as just NO3- ions, the studies below use nitrate nitrogen, to convert their numbers to ours multiply by 4.43.

https://sci-hub.se/https://doi.org/10.1016/j.aquaculture.2017.02.018 [Under 440ppm]

https://sci-hub.se/https://doi.org/10.1111/are.13174 [Under 2200ppm]
'Here, no significant impacts on growth performance, feed conversion and health status were observed between 10 mg L1 NO 3 -N and 500 mg L1 NO 3 -N'

 

[FFGuest6357]

So I have seen the general advice here to always be 'keep nitrates under 20ppm'.
Why? What is this number based on?

Out test kits show nitrates as just NO3- ions, the studies below use nitrate nitrogen, to convert their numbers to ours multiply by 4.43.

https://sci-hub.se/https://doi.org/10.1016/j.aquaculture.2017.02.018 [Under 440ppm]

https://sci-hub.se/https://doi.org/10.1111/are.13174 [Under 2200ppm]
'Here, no significant impacts on growth performance, feed conversion and health status were observed between 10 mg L1 NO 3 -N and 500 mg L1 NO 3 -N'

I love that you’re questioning common wisdom here.

I follow it because it seems to be what has worked based on collective experience that I have researched myself. I’m not going to read those articles right now, because it’s Friday night, and that means beer night.

i will get into them later though, like that your are doing heavy homework. Keep it up.

 

[ClownLurch]

I had fish in the 70s and 90s. I’d never heard of nitrates until last January. Most of the posters on here have forgotten more about fishkeeping than I’ll ever know.
On that basis I’ll go along with the majority opinion though agree it’s good to see the norm challenged every now and then.
I want my fishkeeping to be fun not forensic.

 

[Phreaker]

I am by no means saying we should therefore let our tanks get that high, but having someone with 40 ppm nitrate being told it requires urgent fixing is wrong in my opinion.

 

[mcordelia]

I am glad you are bringing this up for discussion. Maybe @essjay or @Colin_T have sources for why that is the commonly accepted concentration

 

[AbbeysDad]

The general consensus has been <=20ppm - the lower the better.
Nitrates are our only measure of pollution, but there are other pollutants that necessitate routine periodic partial water changes to lower tank nitrates (as well as replenishing necessary minerals used by fish and plants).
Many commercial facilities have auto water change or even flow through systems to ensure the highest water quality. For the most part, with the exception of pollution, nitrates in nature are most often very low or even not measurable. Here is an article that Byron wrote that touches on the desired values: Bacteria in the Freshwater Aquarium
Also, some tips on Lowering Aquarium Nitrates

 

[Phreaker]

I am well aware of the general consensus here, it is that I have yet to see any reason for why this number (or similar values) in particular are ones we should aim for.

 

[xxamyxx85]

This is very interesting, the science behind it baffles me and probably most others, it’s great that you are questioning this, I’m going to sit quiet and wait for the responses, I’m sure it will be a great read.

 

[AbbeysDad]

I am well aware of the general consensus here, it is that I have yet to see any reason for why this number (or similar values) in particular are ones we should aim for.

Deep dive into the science behind keeping aquarium nitrates low.

 

[Phreaker]

Deep dive into the science behind keeping aquarium nitrates low.

That is just a google search link? Is there something I am missing?

 

[kwi]

That is just a google search link? Is there something I am missing?

The articles in the search.
Nitrate in the aquarium (fishtanksandponds.co.uk) Unfortunately the link to the study referenced is broken.
Says maximum safe level is 25ppm.

Nitrates can kill fish (fishtankfocus.com)
Is also worth a read, note in marine tanks 5ppm can devestate marine invertabrates.

There are studies going on all the times and new findings change what we think is best all the time, 40ppm used to be deemed the top end for aquariums, today 25ppm is considered the absolute maximum. 20 years ago if you mentioned Nitrates the response was, "What?"

Fish also respond differently to different levels of nitrates, so surely we should err to the needs of the more sensetive species.

 

[AilyNC]

My tap water is 20ppm. So i just focus on the tank water not rising to 40ppm. It's usually around 30ppm by the end of the week when I'm doing my water change.

I've had losses but mostly just in cycling mayhem. My fish have reproduced with lots of thriving platy fry. My cory have layed eggs that hatched but I leave them in tank so community eh eats them.

I haven't seen issue with nitrate that I'm aware of. But again I do keep an eye to ensure the increase stays between 10 & 15ppm.

 

[Phreaker]

It mentions blindness at 200mg/l nitrate, with no link to the study I would have to assume it is No3-N with would actually be over 800 ppm based on the fact that I have not seen such a low value having such a large impact in any of the studies I reviewed. ( I have checked much more than the 3 that I mentioned in this post).

One more study. https://www.sciencedirect.com/science/article/pii/S0144860917301231
'No important differences were noted between treatments for whole blood gas, plasma chemistry, tissue histopathology, or fin quality parameters suggesting that fish health was unaffected by nitrate concentration' (440ppm again)

 

[Phreaker]

All of these studies also used juveniles for the experiments. Adult fish would have even higher tolerance, while fry is much less tolerant of nitrates.

 

[AbbeysDad]

That is just a google search link? Is there something I am missing?

You can lead a horse to drink, but you can't make him water.
Unlike nature, we contain fish in small glass boxes where the water becomes more and more polluted every day with decaying organic matter. Although we use nitrates as a guide, nitrates keep bad company like phosphates, pheromones, etc...
Nitrates below 100ppm may not be lethal, however, experts tell us that high nitrates reduces the immune system making fish more susceptible to disease, and reduces their life span. Given good care, most tropical fish could live 10-15 years but sadly, the average in the hobby is probably much less.
So the rule of thumb for years now is to keep nitrates below 20ppm...although even lower is better! With rare exception, there's just no such thing as too much fresh water. In fact, fresh water is the very best medicine for fish.
"The solution to pollution is dilution"!