Aquatic Plant Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
49 Posts
Discussion Starter · #1 ·
Hi Everyone,

In her book, Ecology of the Planted Aquarium (Chapter 7), Diana Walstad talks about the use of aquarium plants to take up ammonium from the water. Section 4 within this chapter is entitled "Plants and Nitrifying Bacteria Compete". The essence of this is that plants prefer to uptake ammonium instead of nitrate. So, I did a very basic experiment in order to probe deeper into this...

In an illuminated tank containing Java and Congo Fern, I was able to show that NH4 dropped from 2 mg/litre to 0.4 mg/litre over a period of just four hours! Late yesterday evening, I then added ammonium chloride to raise the NH4 to just under 3 mg/litre and left the tank overnight in darkness. At 12:40 pm today, I measured NH4 and it was still around 3 mg/litre. What could be the explanation for this? Is it because my plants only absorb NH4 in the presence of light, i.e. when the plants are photosynthesizing?

I chose to post here in the Filtration section as I am interested in exploring the use of aquarium plants to possibly replace biological filtration employing nitrifying bacteria.

Any suggestions welcome!

Yorkie
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #3 ·
yes, photosynthesis. Plant do take in other things at night like O2 and I think Phosphate.
Hi mistergreen,

Thanks for your reply.

I am continuing with this experiment. At 1845 this evening, I measured NH4 and it was 1.5 mg/litre. In other words, a 50% reduction from yesterday. I should qualify my use of 'NH4'. It is a JBL NH4 test kit that I'm using but it actually measures total ammonia (NH3 + NH4).

I would like to have Diana Walstad's input on this if she can spare me the time. Is there a way in which I can draw her attention to this thread?

Thanks in advance.

Yorkie
 

·
Super Moderator
Joined
·
7,436 Posts
Hi mistergreen,

Thanks for your reply.

I am continuing with this experiment. At 1845 this evening, I measured NH4 and it was 1.5 mg/litre. In other words, a 50% reduction from yesterday. I should qualify my use of 'NH4'. It is a JBL NH4 test kit that I'm using but it actually measures total ammonia (NH3 + NH4).

I would like to have Diana Walstad's input on this if she can spare me the time. Is there a way in which I can draw her attention to this thread?

Thanks in advance.

Yorkie
Try posting your question on https://www.aquaticplantcentral.com/forumapc/el-natural/
 

·
Super Moderator
Joined
·
2,680 Posts
Hi Everyone,

In her book, Ecology of the Planted Aquarium (Chapter 7), Diana Walstad talks about the use of aquarium plants to take up ammonium from the water. Section 4 within this chapter is entitled "Plants and Nitrifying Bacteria Compete". The essence of this is that plants prefer to uptake ammonium instead of nitrate. So, I did a very basic experiment in order to probe deeper into this...

In an illuminated tank containing Java and Congo Fern, I was able to show that NH4 dropped from 2 mg/litre to 0.4 mg/litre over a period of just four hours! Late yesterday evening, I then added ammonium chloride to raise the NH4 to just under 3 mg/litre and left the tank overnight in darkness. At 12:40 pm today, I measured NH4 and it was still around 3 mg/litre. What could be the explanation for this? Is it because my plants only absorb NH4 in the presence of light, i.e. when the plants are photosynthesizing?

Yorkie
I usually don't check other forums on APC, so I would post your questions there.

Plants take up ammonia as their source of nitrogen for growth both day and night. (Nitrate is only taken up in the presence of light.)

Your plants reduced NH4 from 2 mg/l to 0.4 mg/l in 4 hours. This addition may have saturated their need for nitrogen. Then you added 3 mg/l. Was that immediately after the first reduction?

Plants take up N for growth along with some excess. But there's a limit. There has to be some plant growth involved. Ferns aren't fast growers. You'll notice that most of the scientific testing is done on Elodea, duckweed, Hornwort, etc, not ferns. Usually, scientists doing these studies show that the uptake is accompanied by plant growth.

In an NPT (natural planted tank), growing plants take up ammonia as it is generated in small amounts by natural processes. This means small amounts as they grow.

High concentrations of ammonia are toxic to plants (my book, p. 20), so there's some limit on how much they can take up and how fast.

Currently, I use plants as sole water purifiers in all of my 8 guppy tanks. No filters.

Attached article goes into plant uptake of nitrogen in more detail.
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #7 ·
Your plants reduced NH4 from 2 mg/l to 0.4 mg/l in 4 hours. This addition may have saturated their need for nitrogen. Then you added 3 mg/l. Was that immediately after the first reduction?
I am very grateful for your comprehensive reply - thank you!

With specific reference to the above - yes, the 3 mg/l total ammonia addition was immediately after the first reduction. I was guessing somewhat and, in hindsight, it was too great an increase.

I measured total ammonia at 1900 this evening and it had dropped to 0.2 mg/l. Tomorrow, I'll test total ammonia again and also include NO2 and NO3.

Yorkie
 

·
Super Moderator
Joined
·
2,680 Posts
Sounds like you have a scientific mind-set. Excellent.

The scientists looking for plant uptake of ammonia always check nitrates and nitrites to make sure that the N removal from the ecosystem is not due to nitrification.

Even then, it is hard to sort out. Nitrogen is recycled via many different pathways by many different organisms, bacteria species, etc. Everybody wants nitrogen!
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #9 ·
Sounds like you have a scientific mind-set. Excellent.

The scientists looking for plant uptake of ammonia always check nitrates and nitrites to make sure that the N removal from the ecosystem is not due to nitrification.

Even then, it is hard to sort out. Nitrogen is recycled via many different pathways by many different organisms, bacteria species, etc. Everybody wants nitrogen!
Hello again!

Yes, I have a science degree in electronics but I'm really enjoying my foray into the Life Sciences.

I decided to make a fresh start with the plants and ammonium experiment whilst continuing to use the same tank and plants. So, I did a 100% water change filling the tank with rainwater (as before) with added minerals to raise the conductivity to 200 microSiemens/cm. This is equivalent to 128 ppm TDS. I have also added doses of Flourish Iron, Flourish Phosphorus plus Flourish Trace to cater for the needs of the plants. The remineralizing salts contain calcium, magnesium, potassium, bicarbonate, chloride and sulphate; I use Tropic Marin Re-Mineralize Tropic.

Immediately after setting up this tank, I measured Total Ammonia Nitrogen (TAN), nitrite and nitrate, which were <0.05 ppm, 0.1 ppm and <0.5 ppm, respectively. I have made up a stock solution of NH4Cl and this will enable me to add tiny doses of ammonium to the tank. If necessary, I can reduce the likelihood of any interference from nitrification as there is a small UV-C sterilizer in the tank, which should kill off any waterborne bacteria. This can be switched ON or OFF, as necessary.

Later today, I will re-measure nitrite and, perhaps, TAN plus nitrate.

I will keep you updated.

Yorkie
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #10 ·
Hi Everyone,

I measured nitrite less than an hour ago and it has dropped a little. The JBL NO2 test kit has good resolution and I was able to read the new nitrite figure as 0.05 to 0.1 ppm. The colour match was nearer 0.05 ppm. No other measurements were done other than to check ORP/Redox, which was +230mV, thus indicating good oxygen level in the water.

Yorkie
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #11 ·
Hi Everyone,

Quick Update


Nitrite measured at 1315 today. It is a tad less than 0.1 ppm - so it hasn't changed since yesterday. This comes as a bit of a surprise. The ferns appear to be fine - I will attach a photo in my next post. Water temperature is 25.7C +/-0.2C. I didn't see much point in measuring either ammonia or nitrate at this stage based on the above nitrite figure. Nothing was added to the tank today.

I am unable to measure PAR for the lighting. But, a rough-and-ready check of the spectrum indicates a decent amount of red light, plenty of blue light and much less green. The dominant wavelength appears to be around 450nm. I do have a spectrometer but it's a bit of a pain to set it up. Compared with my other tanks, the light I'm using appears quite bright to my eyes. It is an LED unit that I removed from an Aqua One 30 litre tank. The tank that I currently have the ferns in is a mere 12 litres and is only 20 cm depth.

I realize that my posts will probably be of no interest to most people but I am presenting this data in the hope that Diana Walstad may find time to add any comments.

Yorkie

P.S. Is there a way of including a member's name in a post with the suitable prefix that will alert the appropriate member to the post?
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #12 ·
Hi Everyone,

Two days ago (25/10/20), I added NH4Cl to raise TAN to 1.5 ppm as measured by the JBL 'NH4' test kit. Yesterday (26/10/20), TAN measured 0.4ppm, NO2 measured 1 ppm and NO3 measured between 5 and 15 ppm. Water pH is around 7.3.

I have calculated NH4-N (TAN), NO2-N and NO3-N at the outset and at the end of this exercise. These three parameters total approx. 1.4 ppm in both cases. So, the plants don't appear to have taken up any of the ammonium. Instead, the ammonium appears to have been oxidized to nitrite and nitrate. I conclude that nitrifying bacteria may have effected this oxidation. This is despite my best attempts to eliminate nitrifying bacteria in this tank. As the tank was scrupulously cleaned with KMnO4 solution beforehand (including dipping the plants and the wood to which they are attached) plus the use of UV-C sterilization of the water column, this is not what I had expected. The tank is also illuminated during the day and light is known to inhibit the growth of nitrifying bacteria. There is no substrate.

I need to take a break right now to give my grey matter a rest.

Hope to be back later today. In the meantime, if anyone spots any errors in my reasoning, please let me know.

Yorkie
 

·
Registered
Joined
·
2,338 Posts
Correction. it's 1.5ml/Gallon of 3% H2O2. 1.5ml/L is be too strong for livestock, and some plants.
 
1 - 16 of 16 Posts
Top