redfield ratio

[boxfishpooalot]

106 C : 16 N : (16 Si) : 1 P

Is this the uptake of all marine plants?

After a conatiner test, I found that my chaetomophea takes more phosphate than nitrates.

When zooplankton settle on the ocean floor, they are decomposed and release 106 C : 16 N : 1 P, which is perfect for phytoplankton.

I find that my chaeto consumes more like, 1P : 8N . Why? test error?

[Boomer]

Is this the uptake of all marine plants?

No, it is really the ratio of carbon, nitrogen and phosphorus in phytoplankton.



This will help you understand the Red Fiield Ratio

http://scienceweek.com/2004/sa041119-5.htm

http://www.agu.org/revgeophys/chisho00/node2.html

In FW with calculator

http://www.xs4all.nl/~buddendo/aquarium/redfield_eng.htm

[Randy Holmes-Farley]

What test did you do?

This article shows how much nitrogen and phosphorus are taken up by macroalgae:

http://www.botany.hawaii.edu/Bot482/Kaneohe%20Bay%20algae%20N-P%20Larned%20Mar%20Biol.pdf

It shows total N to total P ranging from 27:1 to 200:1

here my commentary on it from my phosphate article:

http://www.advancedaquarist.com/issues/sept2002/chem.htm

"For those interested in knowing how much phosphorus is being exported by macroalgae, this free pdf article in the journal Marine Biology has some important information. It gives the phosphorus and nitrogen content for 9 different species of macroalgae, including many that reefkeepers maintain. For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % by dry weight phosphorus and 5.6% nitrogen. If one were to harvest 10 grams (dry weight) of this macroalgae from a tank, it would be the equivalent of removing 24 mg of phosphate. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67 gallon tank. All of the other species tested gave similar results (plus or minus a factor of 2). Interestingly, using nitrogen data in the same paper, it would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same tank."

[Boomer]

Nice PDF Randy :D

[Gudwyn]

Has anyone tried dosing nitrate to consume phosphate thru macro growth?

My nitrate is <1ppm and phosphate has no reading on salifert test kits. BB tank. I use carbon and GFO in forced flow reactors. Grow chaetomorphia in fuge, but it doesn't grow fast and seems to get encrusted with coraline.

Anyway, I keep thinking about dosing CaNO3 or KNO3 to force nitrate up to ~2ppm and then grow gracilaria to soak up the phosphate rather than using the GFO and chaeto.

I think that if I dose iron and keep the nitrate detectable, the gracilaria should be phosphate limited. In theory, I would have gracillaria to feed and wouldn't need to buy GFO or nori.

But I'm too chicken to try it... everyone is always talking about nitrates being a problem...

[Randy Holmes-Farley]

Has anyone tried dosing nitrate to consume phosphate thru macro growth?


yes, some people do that if they have very little nitrate and excess phosphate. But I wouldn't if you do not detect phosphate.

I think that if I dose iron and keep the nitrate detectable, the gracilaria should be phosphate limited. In theory, I would have gracillaria to feed and wouldn't need to buy GFO or nori.

I do that with Chaetomorpha and Caulerpa racemosa, but I do not dose nitrate. :)

[boxfishpooalot]

<a href=showthread.php?s=&postid=7494965#post7494965 target=_blank>Originally posted</a> by Randy Holmes-Farley
What test did you do?



ICP of course! :D j/k

Just measured the uptake of nitrate and phosphate in a lit 1 liter container to judge the dowfall of both nutrients.

So far it seems I have to keep adding tap water to it to raise the Po4. Started at about 16ppm nitrate, with .10ppm of phosphate. They used up that phosphate by the next day(24 hour photo p)

So I added another phosphate surge from the tap wich was about .25ppm of Po4, the nitrates appear to be reduced to 10ppm of nitrate.

Although the chaeto is in there,there is a diatom growth on the walls of the container, wich might be doing the work, as I dont see any bubbles from the chaeto but instead the diatoms(photosythesis)

[Randy Holmes-Farley]

Bear in mind that the ratios above are N and P, not nitrate (NO3-) and phosphate (PO4---). :)

[boxfishpooalot]

Well, after a couple more days without testing, surprisingly the nitrates are clear(undectable)and the chaeto has doubled in size. Phosphates are also undetable, wich surprises me too.

Why did the nitrates drop from 10ppm or so to zero while the phosphate was only reading about .25 or so?

Maybee chaeto sucked out the phosphates lower than the Salifert phosphate dectection limits? I thought that the chaeto would be limiting in phosphates due to the higher concentration of nitrates. I probably added about 1ppm of phosphates and started at about 18ppm of nitrates im guessing. Well around 15-20ppm nitrates.maybee less.

I did that little experiment to see if I could house fish without live rock, sand ect and just have a skimmer with large pvc sps covered as decoration. So far it seems good! Macro algae did its job-witout phosphate additons.

Next thing I did to the container with cheato in it is added a chunk of live rock in my tank, to see how much phosphate and nitrates will rise. Then I can prove my rocks are a nutrients sink! And out they will go, maybee.

[Randy Holmes-Farley]

[B]Why did the nitrates drop from 10ppm or so to zero while the phosphate was only reading about .25 or so? [?B]

I wouldn't assume that your kits are exactly accurate, but one does expect nitrate usage to be higher than phosphate usage by a considerable margin. Just because the Salifert test did not detect it does not prove it is limiting.

[boxfishpooalot]

Whats the lowest on the Salifert Po4 test that will show a blue tinge? Is that at or lower than natural reef levels?

Fwiw, I like to do a lot of experimenting like this. But im sick of spending money on test kits that dont get down to the lowest numbers. Also I dont want to read colors, because they are imposible to accurately say that there is 1.0033 ppm of phosphate, as an example.

How does a chemist measure phosphates to the exact number, is there a way like titration(alkalinity) for phosphate? Could I perform an accurate test at home, where I can say my phosphate dropped exactly .23ppm since yesterday? That would be awesome!

[Randy Holmes-Farley]

I do not know what colors you can see. :)

How does a chemist measure phosphates to the exact number

We measure phosphate a lot, and do so in any of several ways depending on the experiment. ICP is used most often, but we also use ion chromatography and are exploring a phosphate electrode (not commercially available).

In my GFO testing experiments I am using a Hach kit. I believe that I can read it +/- 0.02-0.03 ppm. :)

[Habib]

<a href=showthread.php?s=&postid=7492854#post7492854 target=_blank>Originally posted</a> by boxfishpooalot
106 C : 16 N : (16 Si) : 1 P

Is this the uptake of all marine plants?

After a conatiner test, I found that my chaetomophea takes more phosphate than nitrates.

When zooplankton settle on the ocean floor, they are decomposed and release 106 C : 16 N : 1 P, which is perfect for phytoplankton.

I find that my chaeto consumes more like, 1P : 8N . Why? test error?

Besides the other comments, there are other sources for N besides nitrate. Such as ammonium and nitrite. For P, if the inorganic P is very low, they will use extracellular alkaline phosphatase to split organic phosphate esters.


Then there is "luxury uptake" in which the ratio get's skewed by the actual concentration of the nutrients in the water column.

[boxfishpooalot]

Thanks for the information Habib!

Do you think that they obtained phosphate from organics to fully remove the additional nitrate? I did after all add some detritus from the sump of my tank originally, but removed it afterwards. So there is of course organics in the water.

I wonder if macro algae would perform better at organic removal than a skimmer would? Why do we need bacteria again? :lol:

[Habib]

Do you think that they obtained phosphate from organics to fully remove the additional nitrate?

I don't know. :) I doubt one could also exclude the peresence of bacteria, some of them also show luxury uptake.

I recall seeing an abstract (or paper) recently in which phosphate supplementation in a natural reef did result in nitrate reduction.

I wonder if macro algae would perform better at organic removal than a skimmer would? Why do we need bacteria again?

A skimmer is helpful in removing organics before they are broken down. FWIW, macroalgae can outcompete bacteria for ammonium.

[boxfishpooalot]

Ok I added that big rock to the water, wich displaced about 1/3 the water. My tank nitrates are high and phosphates too.

The phosphate and nitrates the next day are Po4 .50-.75ppm . Nitrates are dark purple, probably 100ppm or so.My tank has 3ppm phosphates and about the same for nitrates.

Do you think my rock just added enough water from the main tank to skew it? Or the rock is full of organics and they decomposed to show theese results. How would I know what caused it?

[boxfishpooalot]

Randy, do you think I should do a 100% water change in that container, to see if the rock is organic laden? Wich I could see if nitrates and phosphates raise then.

I just added a big rock to it only to see the nitrates gone too 100ppm and about 1ppm phosphates.

I need to find out if the rocks are rich in organics.

[Randy Holmes-Farley]

Live rock will certainly have lots of orgnaics on it.