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Are nitrates bad in planted aquariums?

Jacob Coleman

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I have a planted tank which is stocked with around 20 small fish, the last couple of times I have tested the water my nitrite has been at 0 but my nitrate has been around 20 on the api test strips, according to the test strips this isn’t bad.

I was wondering weather I should try to lower the nitrate or leave it because the plants can use it to grow?
 

dw1305

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Hi all,

The first thing would be "do the plants and fish look healthy?"

Assuming they do? Then there isn't much wrong with what you are doing at the moment.
I was wondering weather I should try to lower the nitrate or leave it because the plants can use it to grow?
Nitrate (NO3) levels usually go down in a planted tank over time. You probably have <"fairly high NO3 levels in your tap water"> (you can find out from your water supplier), because of where you live. Most of the south and east of the UK has hard water with high NO3 levels.

Personally I don't <"test for nitrate">, I use a different method (the <"Duckweed Index">) for estimating nutrient levels.

Have a read through the linked threads and they should answer most of your questions.

cheers Darrel
 

Jacob Coleman

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I do a 40% weekly water change just to be safe, I am running a Ehiem pro4 350 and it has two trays full of biohome ultimate,Ehiem substrat pro and bio rings so I think it may be something to do with my tap water.
Thankyou for the advice :)
 

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dw1305

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Hi all,
if you post a photo, we can have a look
The plants and fish both look fine.

All three <"Rummynose Tetra species"> are quite sensitive to declining water quality, and don't really like hard water, so the fact that their "noses" are nice and red suggests that there isn't a lot wrong.

You mainly have slow growing plants, you could try adding some faster growing stems and or floating plants. I like floating plants, but I know they aren't to everyone's taste. If you want some, PM me and I can send a mix.
I am running a Ehiem pro4 350 and it has two trays full of biohome ultimate,Ehiem substrat pro and bio rings so I think it may be something to do with my tap water.
Aerobic microbial filtration won't deplete the nitrate (NO3), but your plants will, assuming that other nutrients aren't already limiting plant growth.

The filter media micro-organisms will convert ammonia (NH3) to nitrite (NO2) and eventually NO3. You've gone from three hydrogen (H) to three oxygen (O) so you you've added an acid (3 H+) and you've consumed a base (3 O-). Your water will supply the base (2 CO3-), but it is the <"oxygen that is really important">.

A lot of conversation about biological filter media talks about a possible final stage of the nitrification cycle, where anaerobic denitrification converts NO3 to N2 gas. I'm not a fan of this approach.

Have a look at <"Media set up">, the whole thread is worth a read.

cheers Darrel
 

tam

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I'd only worry if it was steadily increasing - that would imply that you are producing more than your plants/water changes are able to cope with and at some point you'll run into an issue. If it stays steady where it is and everything looks good, don't worry too much.
 

jms127

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Agree with all the above, are you using any type of aquatic plant fertiliser? You may be fine with tap water alone if this is a fairly low tech setup but as plant mass increases the demand for nutrients increases and the waste from fish/ content of tap water may not be enough to provide them.
Have you considered an all in one liquid fertiliser? Delivered at baseline values should be sufficient, but may not be needed yet.
 

Jacob Coleman

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You mainly have slow growing plants, you could try adding some faster growing stems and or floating plants.

I have added hygrophila siamensis 53B and some Amazon sword in the background to increase the plant load and have some faster growing plants reducing algae (which has worked) and to use excess nutrients. This is a learning curve I’m 16 and been keeping aquariums for under a year and only recently started planted aquariums. So thanks for all the advise:)
Also floating plants would be great because that are fast growing.


are you using any type of aquatic plant fertiliser?

Yes I am using Tropica specialised and dosing one pump a day.
 

JMorgan

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Just to add - rummy noses can also get a kind of shiny greenish blob of colour on the top of their heads, especially when they're happy. I mention it because in certain lights it can be quite startling, and having read stuff about how sensitive these fish are to water quality my immediate reaction (some years ago now thankfully) was, "Oh blahblahblahblah I've made them go green!" followed by much panic fuelled searching online!! :arghh:
 

rebel

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Based on your picture I think you need to urgently do























absolutely nothing different. :) Soldier on.
 

_Maq_

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There's a prevailing opinion that high level of nitrates (tens of mg/L) are harmless. While I agree that they hardly inflict noticeable damage on animals, I think differently when it comes to aquatic plants.
I've got a theory on plant nutrition, and hereby I present it to a discussion.
In nature, phosphorus and nitrogen are usually the limiting nutrients. My observation as well as literary sources suggest that almost all plants tolerate low to very low levels of P and N quite well (there are exceptions, par example Echinodorus, some free-floating fast growers, etc.); they adapt their growth rate but suffer no deficiency symptoms. Yet care should be taken not to let N and P fall to zero. Complete lack of phosphorus, in particular, is an invisible killer.
Deficiency symptoms appear not when nitrogen is limiting, but only when nitrogen is in excess relative to other nutrients. Excess of phosphorus seems not to have these consequences. Two points lead me to this assumption:
(1) Some aquarists clearly overdose phosphorus without any apparent drawbacks.
(2) Nitrogen forms an absolute majority (in molar terms) among all nutrients.
In short, nitrogen is the nutrient regulating the growth rate. Light and CO2 certainly exert influence on this but they create just organic carbon which can be used as an energy source, energy reserve, or for growth - if nitrogen is present.
Most aquarists willingly or unwillingly (when their source water contains nitrates) face a situation when nitrogen concentration far exceeds that of natural waters. (I've experimented with "natural" levels of nitrogen - lower than equivalent 1 mg/L nitrate - and faced practical difficulties. It was near impossible to keep nitrogen that low and not to be repeatedly falling to zero at the same time. In this, I've relaxed my strictly "natural" approach, and do not recommend it.)
With nitrogen aplenty, plants want to grow but face difficulties when any other nutrient is in relative deficiency. That's the source of deficiency symptoms. All of them? I rather suspect so.
While reading discussions in this forum (and not only here, of course) I often wonder why so many aquarists struggle with deficiency symptoms while dosing much more and much more often than I do. I admit strong lighting and CO2 injection play their roles, no doubt. I wonder whether CO2 injection could induce deficiency defects if nitrogen is limiting nutrient? I'd really like to know.
Iron, for instance. I'm using only a weak chelate (citrate), and often not even that (iron (III) chloride). My regular amount is 0.017 mg/L (iron content) and I dose it (much) less than once a week. True, some of my plants suffer from iron deficiency, but exclusively in alkaline water (pH = 8), which I accept as part of my experiments. In such cases, adding more iron does not help, anyway. (Advanced chelates might work, though, I've never tried.) In acidic water - all high-tech tanks are in an acidic range, right? - I seldom notice iron deficiency, and can fix it invariably and instantly with one dose of iron citrate or iron chloride.

So, my suggestion is that moderately low nitrogen (2 to 6 mg/L eq. NO3) is the way to avoid most nutrient deficiencies. I'd like to discuss this theory with you, esp. whether you've made any observations which support or contradict it.
(Another side effect - a positive one as I see it - is a reduced growth of fast growing plants, and reduced need of trimming them as a result.)
 

dw1305

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Hi all,
In nature, phosphorus and nitrogen are usually the limiting nutrients. My observation as well as literary sources suggest that almost all plants tolerate low to very low levels of P and N quite well (there are exceptions, par example Echinodorus, some free-floating fast growers, etc.); they adapt their growth rate but suffer no deficiency symptoms. Yet care should be taken not to let N and P fall to zero. Complete lack of phosphorus, in particular, is an invisible killer.
I think that is a fair enough hypothesis, the environment is awash with <"unnatural levels of nutrients">. Personally I'm more interested in the <"lower limit of plant growth">, not the optimal level.

The ability to <"persist at low nutrient levels"> was one of the reasons I swapped to Limnobium laevigatum (from Lemna minor) for the <"Duckweed Index">.

We have talked about different nutrient in terms of <"Orchids, Bromeliads and Tomatoes"> (and <"turned up to eleven"> plants). I really don't think that there is a "one size fits all" nutrient addition.
(1) Some aquarists clearly overdose phosphorus without any apparent drawbacks.
I'm guessing there will be aquatic plants that are damaged by high PO4--- levels (probably via <"luxury uptake">), purely because <"there are terrestrial ones"> that are.

cheers Darrel
 
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Ria95

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DE
I see little need to resurrect a threat that was happily concluded back in 2019.
As far as the theory goes, here are my observations:
(1) Some aquarists clearly overdose phosphate without any apparent drawbacks.
(2) Nitrate is clearly overdosed by some aquarists without any apparent drawbacks.
 

John q

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There's a prevailing opinion that high level of nitrates (tens of mg/L) are harmless.
I think they are harmless @_Maq_ these tanks are dosed with 12ppm No3 weekly (20ppm accumulation) and whilst not perfect the excess nitrate is clearly not causing any issues.
20220829_130841.jpg


20220829_165019.jpg


I see little need to resurrect a threat that was happily concluded back in 2019.
👍
 

plantnoobdude

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17 Mar 2021
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uk
I think there may be a few select plants which despise higher No3 or PO4 levels. Something I might have to try experiment with. I remember a past friend who sold plants that had say 60-80species and dozens of tanks, explained that in their tanks Po4 could be toxic over 10ppm. But I doubt the majority would have any issues as seen by John q s pics above. This would be fairly easy to test, dose NO3 to 60ppm, every water change get it back up to those levels with target dosing. And do the same with Po4, (say 20ppm). And dose like that for a set amount of time, 3-4weeks.

Again, I doubt the majority with easy plants such as crypts, ferns, anubias, easy stems, from I’ll see any difference. A tank full of demanding picky soft water plants, that come from truly nutrient deprived waters? Probably a different story!
 
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