What Is The Best Nitrate Concentration For Plants?

[mark4785]

To stop wastage of fertiliser I'd like to query those who run planted tanks as to the best nitrate level for optimum plant growth.

I use a Horiba Digital Nitrate meter to ensure that I always have nitrate present in the tank water. This meter is extremely accurate and usually indicates a reading of 42 - 46 mg/L of nitrate in my tank water; a level I try to maintain at all times.

But am I maintaining a too higher level? Will I still get plant growth and pearling at say 30 or 25 mg/L?

I'd appreciate your opinions on this matter.


Mark.

 

[snazy]

To stop wastage of fertiliser I'd like to query those who run planted tanks as to the best nitrate level for optimum plant growth.

I use a Horiba Digital Nitrate meter to ensure that I always have nitrate present in the tank water. This meter is extremely accurate and usually indicates a reading of 42 - 46 mg/L of nitrate in my tank water; a level I try to maintain at all times.

But am I maintaining a too higher level? Will I still get plant growth and pearling at say 30 or 25 mg/L?

I'd appreciate your opinions on this matter.


Mark.

Fish wise, it looks a bit high. I would presume that the best level depends on a lot other stuff, like your phosphate levels for example but generally, as long as there's measurable nitrAtes in the water at all times for the plants to uptake, then the exact value shouldn't be of such great importance. I'd keep it at 20.

 

[mark4785]

To stop wastage of fertiliser I'd like to query those who run planted tanks as to the best nitrate level for optimum plant growth.

I use a Horiba Digital Nitrate meter to ensure that I always have nitrate present in the tank water. This meter is extremely accurate and usually indicates a reading of 42 - 46 mg/L of nitrate in my tank water; a level I try to maintain at all times.

But am I maintaining a too higher level? Will I still get plant growth and pearling at say 30 or 25 mg/L?

I'd appreciate your opinions on this matter.


Mark.

Fish wise, it looks a bit high. I would presume that the best level depends on a lot other stuff, like your phosphate levels for example but generally, as long as there's measurable nitrAtes in the water at all times for the plants to uptake, then the exact value shouldn't be of such great importance. I'd keep it at 20.

How does 25 mg/L sound? I once kept the nitrate level at around 15-20 mg/L and I had a multitude of algal growth which included cyanobacteria. I know algae can grow due to flow problems as well so it could have been inadequate flow that equally caused the algae to form.

 

[snazy]

To stop wastage of fertiliser I'd like to query those who run planted tanks as to the best nitrate level for optimum plant growth.

I use a Horiba Digital Nitrate meter to ensure that I always have nitrate present in the tank water. This meter is extremely accurate and usually indicates a reading of 42 - 46 mg/L of nitrate in my tank water; a level I try to maintain at all times.

But am I maintaining a too higher level? Will I still get plant growth and pearling at say 30 or 25 mg/L?

I'd appreciate your opinions on this matter.


Mark.

Fish wise, it looks a bit high. I would presume that the best level depends on a lot other stuff, like your phosphate levels for example but generally, as long as there's measurable nitrAtes in the water at all times for the plants to uptake, then the exact value shouldn't be of such great importance. I'd keep it at 20.

How does 25 mg/L sound? I once kept the nitrate level at around 15-20 mg/L and I had a multitude of algal growth which included cyanobacteria. I know algae can grow due to flow problems as well so it could have been inadequate flow that equally caused the algae to form.

I wouldn't think the algae was caused by the lower nitrAtes, but more likely inbalance with another nutritient. Then again all algae, including cyanobacteria can be caused by lack of flow that in turn would either cause nutritient defficiency and CO2 fluctuations around the tank, so who knows? Otherwise 25mg/L looks fine to me. But I would test the other measurable values in the tank to see how they go.

 

[Ps3Steveo]

The blue green algae you had/have could be caused by any number of things such as very low nitrates, not in your case. But, sometimes it appears with new setups that have had light and ammonia present at some point. Dirty substrates and filters may also bring it on. Poor water circulation is another possible cause.

Check over these things before you fight it so it doesn't return, flow wise you should aim for 10-20 x turnover per hour in a planted tank so check that first then work on the others, once the cause is identified and rectified you can fight it, best off with a 5 day blackout.

 

[aaronnorth]

As long as nutrients aren't limiting there isnt really an optimum level. On a truly unlimited tank the maximum uptake of NO3 by plants is recorded at 20ppm a week. So as long as you are at say 25ppm, I wouldnt worry. Consistency is more important than aiming for an exact figure.
If you got cyanobacteria by lowering the NO3, I wouldnt bother risking it again. Low NO3 or fluctuations in NO3 (or any other nutrient) can cause algae. Fair enough it could have been another cause previously, but isn't it ironic how it come about after lowering the NO3..
Leave it how it is. Your plants are happy, your fish are happy.

Aaron

 

[mark4785]

As long as nutrients aren't limiting there isnt really an optimum level. On a truly unlimited tank the maximum uptake of NO3 by plants is recorded at 20ppm a week. So as long as you are at say 25ppm, I wouldnt worry. Consistency is more important than aiming for an exact figure.
If you got cyanobacteria by lowering the NO3, I wouldnt bother risking it again. Low NO3 or fluctuations in NO3 (or any other nutrient) can cause algae. Fair enough it could have been another cause previously, but isn't it ironic how it come about after lowering the NO3..
Leave it how it is. Your plants are happy, your fish are happy.

Aaron

Thanks for all the contributions to the thread so far.

I have quoted your comment Aaron as I thought I'd get your opinion/response to the claim by Goodwall and Stewart (found here: http/www.cichlid-forum.com/articles/spironucleus.php ) that:

the degradation of vitamin C is accelerated in the presence of light, oxygen, heat, copper, a base ( pH over 7.2 ) solution and high nitrate levels.

Also add to this UV-steralisation.

I thoroughly agree with you that the fish I have now are 100% happy and don't mind the nitrate level of approximately 45 ppm; the fish I have are black neon tetras and two pairs of Corydoras. But what about sensitive dwarf cichlids like the German Blue Ram and other cichlids which the above mentioned report seems to imply that certain nitrate figures will bring on stress and then hole-in-the-head syndrome?

Every German Blue Ram that I have owned has succumbed to hole-in-the-head in its later life and I'd really like to get to the bottom of what is causing it! Ammonia and nitrite levels are always 0 ppm, KH and GH are always low and PH is around 6.0. So these parameters are all at optimum levels. This fish doesn't live in a high-light, high-nitrate and high-co2 river basin. What IF ANY of these parameters do you (or any other forum members) think could cause an illness in excess?

Many thanks!

 

[mark4785]

Fish wise, it looks a bit high. I would presume that the best level depends on a lot other stuff, like your phosphate levels for example but generally, as long as there's measurable nitrAtes in the water at all times for the plants to uptake, then the exact value shouldn't be of such great importance. I'd keep it at 20.

When I do a W/C the level usually drops from 45 ppm to about 30 ppm. But I feel a bit on edge to not gradually top it back up to 45 ppm with ferts by the time the next W/C is due because I have no idea what proportion of the 30 ppm is organic-produced (i.e. the nitrogen cycle could have produced 15 ppm of it from cycling ammonia and nitrite into nitrate). Is there any downside to relying on organic nitrate to some degree?

I'd be very interested to take your tank specs (specifically whether you are using pressurised co2 or not, the light intensity and your nitrate level) IF you are running a planted-tank with 20 ppm of nitrate as this will give me a good idea as to how similar your tank is to mine and therefore how likely it is that I can sustain plant growth with relatively lower nitrate levels.

 

[snazy]

Why would there be any downside to organic nitrAtes? One of the points of having plants is to control the nitrAte to a level suitable for the fish. Plants also take up ammonia and nitrIte from the water. NitrAte is their least desirable source of food but in a cycled tank they'd have to I guess.
The point of adding extra NitrAtes is if you have a heavily planted tank with pressurized CO2, because the plants may use all of the one produced by fish. You don't need to dose nitrAtes if your tank is heavily stocked with fish and naturally your nitrAte levels before a water change are at 30-40ppm(that's if your test is accurate) If lowering your nitrAte levels to 20-25ppm is causing algae issues, then you may have an issue with phosphate to nitrAte proportion for example. You will have algae issues if your nitrAte levels go to 0 without you noticing, then the algae will use up the available free phosphates. Same if there's a disbalance between the nitrAtes and phosphates which I think should be in 10:1 or even 20:1 nitrate to phosphate level. Are you dosing phosphate too? Phosphate levels in a heavily stocked tank via fish food can rise up pretty quick, also your tap water may contain a good amount. When you had the algae problems was it all solved by upping up the nitrAte levels? If so, why fix it as dosing up nitrAtes may not be affecting the fish at all at the end of the day. If you still have an issue with algae, then what type of algae did you have on top of cyanobacteria as this can tell you what you are lacking on in the tank.


And to check what proportion of the ppm nitrAte is organic produced, why not test the nitrAte in the tank before dosing nitrAte and after one dose of nitrAte. With such an accurate nitrAte reader it will give you exactly how much ppm nitrAte you just dosed up by substracting the second reading from the first before you dosed. And then multiply this by the days dosed per week, it will give you your weekly nitrAte doses. Then substract that from the total nitrAte in the tank before a water change and the remainder should be the organic nitrAte produced by fish.

 

[SO19Firearms]

Why would there be any downside to organic nitrAtes?

You will have algae issues if your nitrAte levels go to 0 without you noticing, --
-- Same if there's a disbalance between the nitrAtes and phosphates which I think should be in 10:1 or even 20:1 nitrate to phosphate level.

Downside to organic nitrate is how it gets there - The oxygen theft involved tends to become a problem. Before we were adding Nitrate the test kit showed that at (x)ppm we're getting sick fish and this £10 I just spent tells me its the Nitrate levels....keep re-regurgitating that for a few years and it becomes fact.... IMO

I'm not sure the balance and ratio stuff...it sounds more like the often-disproved Redfield ratio than the more sound (IMO) Liebig's law of the minimum.


IMO

 

[snazy]

Why would there be any downside to organic nitrAtes?

You will have algae issues if your nitrAte levels go to 0 without you noticing, --
-- Same if there's a disbalance between the nitrAtes and phosphates which I think should be in 10:1 or even 20:1 nitrate to phosphate level.

Downside to organic nitrate is how it gets there - The oxygen theft involved tends to become a problem. Before we were adding Nitrate the test kit showed that at (x)ppm we're getting sick fish and this £10 I just spent tells me its the Nitrate levels....keep re-regurgitating that for a few years and it becomes fact.... IMO

I'm not sure the balance and ratio stuff...it sounds more like the often-disproved Redfield ratio than the more sound (IMO) Liebig's law of the minimum.


IMO

I meant organic nitrAte as a source of plant nutritient. Other than that I guess there's a more lot to it than just a straight forward explanation.

 

[mark4785]

Why would there be any downside to organic nitrAtes? One of the points of having plants is to control the nitrAte to a level suitable for the fish. Plants also take up ammonia and nitrIte from the water. NitrAte is their least desirable source of food but in a cycled tank they'd have to I guess.
The point of adding extra NitrAtes is if you have a heavily planted tank with pressurized CO2, because the plants may use all of the one produced by fish. You don't need to dose nitrAtes if your tank is heavily stocked with fish and naturally your nitrAte levels before a water change are at 30-40ppm(that's if your test is accurate) If lowering your nitrAte levels to 20-25ppm is causing algae issues, then you may have an issue with phosphate to nitrAte proportion for example. You will have algae issues if your nitrAte levels go to 0 without you noticing, then the algae will use up the available free phosphates. Same if there's a disbalance between the nitrAtes and phosphates which I think should be in 10:1 or even 20:1 nitrate to phosphate level. Are you dosing phosphate too? Phosphate levels in a heavily stocked tank via fish food can rise up pretty quick, also your tap water may contain a good amount. When you had the algae problems was it all solved by upping up the nitrAte levels? If so, why fix it as dosing up nitrAtes may not be affecting the fish at all at the end of the day. If you still have an issue with algae, then what type of algae did you have on top of cyanobacteria as this can tell you what you are lacking on in the tank.


And to check what proportion of the ppm nitrAte is organic produced, why not test the nitrAte in the tank before dosing nitrAte and after one dose of nitrAte. With such an accurate nitrAte reader it will give you exactly how much ppm nitrAte you just dosed up by substracting the second reading from the first before you dosed. And then multiply this by the days dosed per week, it will give you your weekly nitrAte doses. Then substract that from the total nitrAte in the tank before a water change and the remainder should be the organic nitrAte produced by fish.

Response to above points:

My nitrate level is not naturally 30-40 ppm before a W/C. I actually artificially, through dosing, reach this level of nitrate.

I think I had algal problems (cyanobacteria, green dust algae and green spot algae) when my BPS rate was too low and co2 flow was bad. At the time of the cyanobacteria, I tested my nitrate level with an ordinary API test kit (I didn't have the scientific nitrate meter then) and it indicated a concentration of between 10 - 15 ppm. I was quite anti-nitrate THEN so I never used a nitrate fertiliser. NOW I know I need nitrate desperately to grow plants but I want to know what the lower-limit is for sustaining plant growth, good fish health and no algae. I know 45 ppm in my tank achieves good plant growth and no algae; but I'm not sure the M.ramirezi flourishes in high nitrate water. The beauty of having a scientific instrument that monitors nitrate levels accurately is that it won't give me a false reading, allowing me to more closely hover to a lower-limit nitrate concentration without risk of having a deficiency.

I think my nitrate to phosphate ratio is around 10:1. My nitrate level is usually around 45 ppm, whereas the phosphate level is usually 3 ppm (this is not an accurate phosphate reading though as I just test it using a regular testing kit); I do indeed dose phosphate.

There are no algae issues at present under the current tank conditions. I want to keep it like this but with a bit less nitrate for reasons relating to what the report that I have provided a link to (see my prior posts) states.

 

[snazy]

Someone may say differently but your phosphate levels, although still ok, are a bit too high. Maybe that's why lowering the nitrAte has caused algae. As already mentioned, the most common, ideal nitrAte level is about 20ppm. That would give you max 2ppm phosphate allowance and even 1ppm should be plenty enough for plant growth?

 

[SO19Firearms]

Someone may say differently but your phosphate levels, although still ok, are a bit too high. Maybe that's why lowering the nitrAte has caused algae. As already mentioned, the most common, ideal nitrAte level is about 20ppm. That would give you max 2ppm phosphate allowance and even 1ppm should be plenty enough for plant growth?

Yeah, not sure I agree.
Where do these ratios and levels come from?

 

[Ps3Steveo]

Yeah can't say I've heard that ratio before as correct level, i read a minimum of 1:10 at least.