Nitrates and plants

Adams92

New Member
Since my switch from artificial plants to live plants I have been researching various things on the internet; one of which I came across the other day which was to do less water changes in order to keep nitrate levels moderate-moderate high for plant growth. Wondering about people’s experience with this as it kind of went against my knowledge so far which is to keep them low/very low. Many thanks.
 

mrsP

Well Known
I have hevily planted tank, and do my water changes as usual. And plants still grow like weeds.
 

RDcompton03

Active Member
My tank is heavily planted and i keep my nitrates on the higher side. With 10% water changes a week. It seems a bit pointless to do a water change to lower nitrates and then put ferts back in containing nitrates.
 

wishuponafish

Well Known
As long as your nitrate is constantly above 0 it means the plants have enough and aren't using it up faster than it's produced, so you don't have to keep it exceptionally high or anything.
 

Chanyi

Well Known
My tank is heavily planted and i keep my nitrates on the higher side. With 10% water changes a week. It seems a bit pointless to do a water change to lower nitrates and then put ferts back in containing nitrates.


Wrong, water changes remove / replenish several other plant nutrients and other elements that can lead to a successful planted tank.

Including, but not limited to:
Nitrates
Phosphates
Calcium
Magnesium
Excess organic material in the tank
Chelated micro nutrients that may have precipitated out of solution / are not plant available

As long as your nitrate is constantly above 0 it means the plants have enough and aren't using it up faster than it's produced, so you don't have to keep it exceptionally high or anything.

Wrong, certainly all plants would prefer a given NO3 level. Some prefer it higher, others prefer it lower. Having any NO3 level is not the best way at approaching plant nitrogen needs, especially when there are several plant species in the tank. It also strongly depends on how much energy is being thrown at the tank. Higher growth speeds require more NO3, lower growth speeds require less (but not always) NO3 levels.

There is no once-size fits all in the world of planted tank. All tanks are different and they all respond different to various fertilizing regimes.
Since my switch from artificial plants to live plants I have been researching various things on the internet; one of which I came across the other day which was to do less water changes in order to keep nitrate levels moderate-moderate high for plant growth. Wondering about people’s experience with this as it kind of went against my knowledge so far which is to keep them low/very low. Many thanks.


Keep up with regular water changes, ensure you are removing as much organic waste as possible, and crack the filter opens often to clean them out as well. Rotting organics are nothing but algae food, and fertilize for the plants. This way you are limiting the things that can allow algae to thrive, and supplying the plants with exactly what they need.

You can make fertilizing as easy or as hard as you like, there are many options available. Thrive is an easy all in one, EI or PPS-Pro is an easy dry fertilizer regime to follow, or you can get each ingredient individually and go completely custom with all your plant nutrients. Like I said, as easy or as hard as you like it.

Best of luck.
 

RDcompton03

Active Member
Wrong, water changes remove / replenish several other plant nutrients and other elements that can lead to a successful planted tank.

Including, but not limited to:
Nitrates
Phosphates
Calcium
Magnesium
Excess organic material in the tank
Chelated micro nutrients that may have precipitated out of solution / are not plant available



Wrong, certainly all plants would prefer a given NO3 level. Some prefer it higher, others prefer it lower. Having any NO3 level is not the best way at approaching plant nitrogen needs, especially when there are several plant species in the tank. It also strongly depends on how much energy is being thrown at the tank. Higher growth speeds require more NO3, lower growth speeds require less (but not always) NO3 levels.

There is no once-size fits all in the world of planted tank. All tanks are different and they all respond different to various fertilizing regimes.

You are quick to tell everyone else that they are wrong in their opinion and then go on to to say. "There is no once-size fits all in the world of planted tank. All tanks are different and they all respond different to various fertilizing regimes." There seems to be a lot you could learn by being open minded and listing to the experience of others without thinking everyone who doesnt do it your way is wrong.
 

wishuponafish

Well Known
Wrong, certainly all plants would prefer a given NO3 level. Some prefer it higher, others prefer it lower. Having any NO3 level is not the best way at approaching plant nitrogen needs, especially when there are several plant species in the tank. It also strongly depends on how much energy is being thrown at the tank. Higher growth speeds require more NO3, lower growth speeds require less (but not always) NO3 levels.

NO3 levels should be looked at as rates, not a pool.
-NO3 is constantly being produced in your aquarium at some rate dx/dt (dependent on fish/waste)
-NO3 is constantly being absorbed by the plants at some rate dy/dt. That depends on how fast the plants are using it, and plants will only use as much NO3 as they can process.

The rate dy/dt depends on other factors such as type of plant, lighting, CO2, etc. and the plant needs a balance of all of those things to process NO3. That's why a high light high CO2 tank requires and uses more nutrients than low light low tech.

What you see when you test the water for nitrate is simply a snapshot of x minus y, the difference between total NO3 produced and total NO3 consumed, meaning just excess nitrate.

If you measure your NO3 and you get 10 ppm, it just means more NO3 has been produced than consumed, the fish could have produced 40ppm and the plants could have consumed 30ppm or it could be 100ppm and 90 ppm, you don't know.

The NO3 measured in the water is just excess not being used by the plants and it's just harming the fish. Having low amounts like 20-40ppm will give you a buffer for when the plants start consuming more but keeping high amounts provides no worthwhile benefit. It's like having 100 rolls of toilet paper under your sink when you use 1 roll a week.
 

cmid21

Active Member
NO3 levels should be looked at as rates, not a pool.
-NO3 is constantly being produced in your aquarium at some rate dx/dt (dependent on fish/waste)
-NO3 is constantly being absorbed by the plants at some rate dy/dt. That depends on how fast the plants are using it, and plants will only use as much NO3 as they can process.

The rate dy/dt depends on other factors such as type of plant, lighting, CO2, etc. and the plant needs a balance of all of those things to process NO3. That's why a high light high CO2 tank requires and uses more nutrients than low light low tech.

What you see when you test the water for nitrate is simply a snapshot of x minus y, the difference between total NO3 produced and total NO3 consumed, meaning just excess nitrate.

If you measure your NO3 and you get 10 ppm, it just means more NO3 has been produced than consumed, the fish could have produced 40ppm and the plants could have consumed 30ppm or it could be 100ppm and 90 ppm, you don't know.

The NO3 measured in the water is just excess not being used by the plants and it's just harming the fish. Having low amounts like 20-40ppm will give you a buffer for when the plants start consuming more but keeping high amounts provides no worthwhile benefit. It's like having 100 rolls of toilet paper under your sink when you use 1 roll a week.
Right!
 

Chanyi

Well Known
You are quick to tell everyone else that they are wrong in their opinion and then go on to to say. "There is no once-size fits all in the world of planted tank. All tanks are different and they all respond different to various fertilizing regimes." There seems to be a lot you could learn by being open minded and listing to the experience of others without thinking everyone who doesnt do it your way is wrong.

Of course there is always something to learn. I was speaking towards the comment of "any level of NO3 above 0 is good" or "waterchanges are pointless if you are going to dose NO3 back up" each and every tank is different, having 5 ppm in one tank will have vastly different outcomes in another tank.

Only reason I have grown in this hobby was by listening to other people experiences, struggles and success's. If it weren't for those people I had followed, I would have learned only by personal trial and error (which would have taken 10x as long).

NO3 levels should be looked at as rates, not a pool.

While I agree with how it works, striking a balance of consistency in terms of nutrient availability (for some, not all), CO2 levels and lighting levels seems to be a major key in keeping plants thriving. Starting the week with 30ppm and ending at 60ppm seems to spring up issues that are quickly dismissed by the aquarist.

And, some plants might prefer low NO3 while others prefer high NO3 in the same tank, if they can only uptake x amount of water per day, they will uptake more nitrogen per day in a tank at 20ppm than in a tank at 5ppm. Plants aren't selective in what nutrients they can pull from the water.

That is where I have seen the most success, consistent levels being maintained each and every day. The most success I have personally had was when my waste production + dosing = plant uptake. Worked out to be 20ppm.
 

86 ssinit

Fishlore Legend
With just a planted tank yes change as little as you want. But once you add fish it’s a different thing. Asa rule of thumb and fish tank should get a 50% water change a week. Planted included. Many other minerals are added to the water during a water change. Plants eat these. I never check nitrates they just don’t matter. Plants need food and light and clean water to grow strong in our community tanks.
I don’t get the reason to not change water. It’s like walking the dog cleaning the litter box or bird cage. It’s got to be done.
My 125 50% every 2 days.
72E52BF2-F508-47EB-B8E0-3E1171B507D4.jpeg
 

JimC22

Active Member
The thing is every tank is different based on so many variables that there will never be a standard rule. There will be debate about which way to go as everyone has different experiences with varying results. My experience is that water changes are and should be an essential item that it is a primary maintenance item for keeping a consistently healthy tank.

Low nitrates with a FO tank are ideal but having a planted tank changes the way of thinking where having higher nitrates is okay for the health of the plants. Again too many variables that how to manage the tank is why it is its own ecosystem.

I have a heavily planted tank, CO2 with high lights. I still do weekly water changes (>30%). Nitrates are always on the high side due to the plant and fish waste, I do daily dosing with ferts so this also adds to the nitrate levels. The fish/plants are doing fine. I control the nitrates by doing water changes to keep them at or below moderate high level. I'm still dialing in on the ideal level for the tank.

You will want to want to figure out what works best for your tank. Your plants and fish will let you know if they are happy. Testing and water changes are still what I consider needed and should be done to maintain a consistent steady/healthy tank.

Good luck with what you decide on doing.
 

flyinGourami

Well Known
I would still do water changes since plants actually benefit from them. they often will pearl after a water change; water changes are also good for your fish. Your tank(assuming you have fish) should have enough nutrients for your plants unless you have lots and lots and lots and lots of floating plants or something. Tanks that are cycled very rarely will have 0 nitrates, doing water changes can also replenish stuff for plants. I'm not very experienced with plants though so don't quote me on this lol.
 

Tallen78

Well Known
Hey y’all I’m new to the hobby started this year so I’m 6 months in and have done more reading and research than I did my whole schooling venture anyway I have a few planted tanks that have grown well but I have a question what happens when my tanks have no more nitrates in them ?they used to hang around 10-20ppm and the last 2 weeks I always test before water changes I’m getting no nitrates what do I do and should I be worried
 

Mike1995

Well Known
You could add some seachem nitrogen. I do it periodically for my 20g. It runs out of nitrates because of the large amount of plants and low stocking.
Or as long as theres no ammonia or anything you could ease off the water changes for little while, and see if nitrates build up a bit. only thing is if you top your tank off from evaporation, the tanks ph gets lower so monitor that.
 

GlennO

Well Known
Plants do need nitrates but more info would be helpful. How heavily are the tanks planted? What sort of plants? How often and how much water do you change? What sort of fertiliser do you use, if any?
 

Tallen78

Well Known
You could add some seachem nitrogen. I do it periodically for my 20g. It runs out of nitrates because of the large amount of plants and low stocking.
Or as long as theres no ammonia or anything you could ease off the water changes for little while, and see if nitrates build up a bit. only thing is if you top your tank off from evaporation, the tanks ph gets lower so monitor that.
Ok thanks that was going to be my next question if I should hold off on the wc now this nitrogen will it show on tests as nitrates? Or does it strictly act as plant food
 

Tallen78

Well Known
Plants do need nitrates but more info would be helpful. How heavily are the tanks planted? What sort of plants? How often and how much water do you change? What sort of fertiliser do you use, if any?
Ok I’m not sure of the names of all the plants we pretty much just grabbed them I can post pics of all three tanks in question I do weekly wc normally 50% just to replenish nutrients in the water I use flourish and iron twice a week and I use excel and flourish advanced every other day the plants are all doing well some I’ve trimmed a ton of times already but as of last weeks water change I’m reading no nitrates it’s not all the way yellow but not orange enough to get a reading so maybe around 1or2 so I’m guessing my plants are eating it faster than I’m producing it
 

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GlennO

Well Known
Yep I think what you suspect is correct based on the plants, ferts, stock load & water changes. Nice tanks btw. You could do as the above poster suggested and add nitrogen separately however it's possible that you're also lacking phosphates in which case you'll need to add phosporous as well. Or switch to an all-in-one fertiliser that contains nitrates & phosphates.
 

Tallen78

Well Known
Yep I think what you suspect is correct based on the plants, ferts, stock load & water changes. Nice tanks btw. You could do as the above poster suggested and add nitrogen separately however it's possible that you're also lacking phosphates in which case you'll need to add phosporous as well. Or switch to an all-in-one fertiliser that contains nitrates & phosphates.
As to using phosphate I’m hearing u have to dose that alone due to the fact it will bind with other additives like iron and such causing issues in the water is there any truth to that
 

Tallen78

Well Known
As to using phosphate I’m hearing u have to dose that alone due to the fact it will bind with other additives like iron and such causing issues in the water is there any truth to that
And thank u I enjoy the tanks a lot
 

GlennO

Well Known
I can't help you with the science behind it but there are many very well regarded all-in-one ferts that contain phosphates.
 

GlennO

Well Known
If you're going to add them separately, aim for a nitrate to phosphate ratio of 10:1.
 

Mike1995

Well Known
It looks like you have hortwort or anacharis plants in your tank. If its hornwort, that particular plant sucks up a lot of nitrates. So that maybe be whats going on.
 

Tallen78

Well Known
It looks like you have hortwort or anacharis plants in your tank. If its hornwort, that particular plant sucks up a lot of nitrates. So that maybe be whats going on.
Yes it is hornwort I have a few bunches of it in each I have a little of everything some of my plants I purchased as bulbs and they have grown amazing
 

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Mike1995

Well Known
Yes it is hornwort I have a few bunches of it in each I have a little of everything some of my plants I purchased as bulbs and they have grown amazing

That's probably why you have no nitrates. those particular plants are really good at utilizing nitrates quickly. I'd definitely look into a nitrogen to dose.
 

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