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Nitrate Consumption


  1. What was the BEST (nitrate removing) PLANT for YOU ?
    by (W. Keith Newsom-Stewart) (1 Apr 1994)
  2. Re:Use of nitrate
    by (Paul Krombholz) (Sat, 1 Jul 1995)
  3. re: Use of nitrate
    by "shaji (s.) bhaskar" <> (Mon, 3 Jul 1995)
  4. Nitrogen enrichment
    by Neil Frank <nfrank/> ()
  5. Nitrogen
    by eworobe/cc.UManitoba.CA (Thu, 10 Dec 1998)

What was the BEST (nitrate removing) PLANT for YOU ?

by (W. Keith Newsom-Stewart)
Date: 1 Apr 1994

I have recently done a bit of a literature search on N removing plants.
Here are a few things I found:

Reddy and De Busk, 1985, Nutrient Removal Potential of Selected Aquatic
Macrphytes, J. Environmental Quality, 14(4) 459-462.

Nitrogen and Phosphorous Removal in mg/meter square/day.

Eichhornia 1278 243
Pistia stratiotes 985 218
Hydrocotyle umbellata  365 86
Lemna minor 292 87
Spirodela polyrhiza 151 34
Azolla 108 33
Salvinia rotundifolia 406 105
Egeria densa 125 48

These figures are for plants growing in the summer in outdoor containers
of 700 - 900 liters.  The figures are for N and P uptake by plants alone
not for N and P removed by other parts of the system, ie denitrification, 
or anything else.  The data are part of a larger table.  For comparison,
Adey states that an algae scrubber can remove 300 - 1200 mg N/meter square/
day. (p. 231).  George once posted the removal rates for his coil
denitrifier - I forget how it compared.

On the above figures for N removal, note that Nitrate was mostly being 
taken up as the ammonia was rather rapidly converted to Nitrate.  Initial
N concentration in the water was 26 to 29 mg/l, 50% NH4 and 50% HO3.  
Initial conc of P was 3.1 to 3.3 mg/l.  It was not clear to me how low 
a concntration on N and P the various species would achieve.  One interestin
point is that the Azolla will fix its own N from atmospheric, so it can
remove P from systems with no N.  Some research showed that N became limiting
before P so the Azolla would be useful in such systems.

I have about a dozen other articles on the topic that I have not yet had a 
chance to read.  I am swamped and probably won't get to them until summer.

Kitoh, etal. 1993. The growth and nitrogen fixation of Azolla filiculoides
in polluted water.  Aquatic Botany, 46 129-139.

Sytsma and Anderson, 1993, Biomass, N, and P allocatin in Parrotfeather
(Myriophyllum aquaticum), J. Aquatic Plant Management, 31 244-248.

Stott and Wright, 1991, Sewage treatment with plants, a Review.  Letters
in Applied Microbiology, 12, 99-105.

Oliver, 1993, A review of the biology of giant Salvinia (Salvinia molesta),
J. Aquatic Plant Management, 31: 227-231.

Reddy, etal, 1987, The role of Egeria in removing N and P from nutrient 
enriched waters, J. Aquatic Plant Management, 25:14-19

All of these articles have lots of citations.  

The last article in the list stated that 
85 - 97% of initial Nitrate was removed after 7 days in tank.  Initial was
1-4 mg/l.  There seem to be a number of qualifications however.

Keith Newsom-Stewart
Biometrics Unit
Cornell University


Re:Use of nitrate

by (Paul Krombholz)
Date: Sat, 1 Jul 1995

>Date: Fri, 30 Jun 95 18:47:42 CDT
>Subject: Do plants use nitrate?
>Hi Everyone,
>I've just had a discussion with my local store owner after reading a post
>from George Booth saying how Echinodorus may like high-ish nitrates (10-20
>ppm).  My store owner says plants don't use nitrates, they use ammonia -
>is he correct?
>I was thinking Geroge was right, particularly since my swordplants have
>never done particularly well (look OK, just haven't grown nearly as big
>as their parents).  Mine were in a 125 gal tank with UGF and nitrates
>0-4 ppm.  I have now moved them to tanks without UGF & higher nitrates.
>Their parents are in a 110 tank with laterite & UG heating (owned by the
>store owner).
>Also ... I was wondering if anubias might need nitrates also.  My anubias
>did poorly when I reduced nitrates in their 25 gal tank, but this kind of
>coincided with anaerobic substrate & they just disintegrated :-(.
>Any comments would be appreciated.  Hopefully I'll be in the fishroom
>tomorrow & maybe we can discuss this there.

Hi Joanne.  Aquatic plants do very well on nitrates.  I once grew 8 genera,
including Vallisneria, Elodea, Ceratophyllum, and even Aponogeton
madagascareinsis, in sterile culture,(well, almost sterile, at least
algae-free), in flasks with nitrate as their only source of nitrogen.  They
all grew very rapidly and used up all the nitrate supplied.  This is not to
say that they can't also use ammonia.  I believe that if you have
measurable nitrate, even as low as 1PPM, that should be plenty for your
plants.  If the plants aren't doing well, look to other needs, nutrient, or
otherwise.  With UGF, iron deficiency is likely to occur.  I grow my plants
in soil or a soil-gravel mix, with no filtration of any kind.  I am sure
that Anubias can use nitrates also.  Anubius is one type of aquatic plant
whose roots do not appear to be adapted for living in anaerobic mud.  I
have noticed that Anubias does almost as well floating as rooted, and that
Anubias roots tend to attach to stones and gravel the same way that the
modified roots of ivy cling to stone.  For Anubias, I would put just a
small amount of soil (like 1/4 inch) at the bottom, and then have about 1.5
inches of gravel.

Paul Krombholz

re: Use of nitrate

by "shaji (s.) bhaskar" <>
Date: Mon, 3 Jul 1995

>From: (Paul Krombholz)
>Date: Sat, 1 Jul 1995 17:20:12 +0600
>Subject: Re:Use of nitrate
>Hi Joanne.  Aquatic plants do very well on nitrates.  I once grew 8 genera,
>including Vallisneria, Elodea, Ceratophyllum, and even Aponogeton
>madagascareinsis, in sterile culture,(well, almost sterile, at least
>algae-free), in flasks with nitrate as their only source of nitrogen.  They
>all grew very rapidly and used up all the nitrate supplied.  This is not to
>say that they can't also use ammonia.  I believe that if you have
>measurable nitrate, even as low as 1PPM, that should be plenty for your

I think I can add some information on the ammonium vs. nitrate debate.

About a year ago there was an article by Diana Walstad that said something
to the effect that aquatic plants preferred ammonium over nitrate.

She based her article on a peer-reviewed publication that cited
results from a study done with Spirodela (a kind of large duckweed).
This floating plant was grown in a mix of equal concentrations of
ammonium, nitrite and nitrate.  Tests showed that the ammonium was
absorbed first, and nitrate last.  Nitrate *was* used up, but only
after practically all the ammonium ions were gone.

I'll agree with Paul that as long as some nitrates are present, the
plants are probably not lacking in N.  As he implies, it is possible
to take the "lower is better" dogma too far.  If nitrates read zero,
you probably should be adding some nitrogen.

- -Shaji
- -------------------------------------------------------------------------
Shaji Bhaskar                                    
BNR, 35 Davis Dr., RTP, NC 27709, USA                      (919) 991 7125

Nitrogen enrichment

by Neil Frank <nfrank/>

>Date: Sat, 7 Mar 1998 06:59:04 +1000
>From: David Aiken <>
>Subject: Re: Aquatic Plants Digest V3 #123
>>From your description, the water in the river was obviously (as far as 
>the algae were concerned) nitrogen limited until they got the water from 
>the new stream coming in. Once that happened algae were able to really 
>get a go on - prior to that the plants had the upper hand in utilising 
>all of the nutrients to their advantage.
>Two major nutrients for plants and algae are phosphorus and nitrogen. The 
>experience or people on this list and elsewhere seems to be (gross 
>simplification) that phosphorus limitation is more important than 
>nitrogen limitation in avoiding algae. In other words, you can have 
>higher nitrate levels without algae if you have extremely low to 
>unmeasurable phosphorus levels. 

I would like to add a few things to David's nice explaination. 

Nitrogen limitation can occur in aquaria as in Rivers. An aquarium with a
lot a fast growing plants and a limited addition of fish food can become
nitrogen limited... this can mean 0 nitrates and not enough ammonia to
allow the plants to substantially multiply.  On the other hand, phosphates
are usually in sufficient supply because fish food supplies lots and
phosphates are available both directly from the water and from the
storehouse of the substrate (especially in substrates of tanks with
laterite, soil whose iron binds it and allows it to accumulate). Therefore,
extremely low or even non-detectable concentrations of phosphates are
sufficient to supply plants and feed algae. 

Algae are different from plants in that they depend exclusively on
phosphates in the water. So when the tank (or river) is nitrogen limited,
supplying nitrogen (assuming everything else is sufficient) speeds up the
growth rate of both plants and algae... In an aquarium, however, the more
quickly growing plants will soon pull enough phosphates out of the limited
amount of water to reduce the water column concentration .... which in turn
will starve the algae. Now the plants have the upper hand, they will
continue to suck phosphates and other nutrients, which help keep the algae
from reestablishing.

As David describes, this does not happen with nitrogen enrichment in the
nitrogen limited river whose moving water provides an effectively larger
supply of nutrients.....

Although what David says is true --
>a 10ppm nitrogen level in a river has an 
>astronomically greater impact than a 10ppm nitrogen level in an aquarium..... may not be the larger AMOUNT of available nitrogen or the increased N
to P ratio, but instead a new ADEQUATE supply of nitrogen to the river.
This, in combination with the larger effective (essentially infinite)
supply of phosphates in the moving water (say, from the upstream sediment)
provide the necessary macronutrients to continue to feed the algae. 

Neil Frank, AGA


by eworobe/cc.UManitoba.CA
Date: Thu, 10 Dec 1998

There are no experimental studies (as far as I know) that indicate 
aquatic plants are unable to use nitrate. There are several studies, 
however, that 
indicate clearly that aquatic plants CAN utilize nitrate. Some of these 
studies also show that ammonia(um) is preferentially absorbed. This makes 
sense due to the high metabolic cost of reducing nitrate.


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