Required Nutrient Ratios Appear to be a Myth

[ceg4048]

Hello,
For some time I subscribed to the belief that a 10:1 ratio of NO3O4 was necessary but as I have monitored my nutrient levels during my attempt at EI dosing I've seen this ratio fall or rise far outside this value as I've monitored. I realize idea is to NOT have to test due to poor accuracy but I do anyway just as a monitor and to try to understand the numbers (perhaps the kits are all a placebo).

In any case I've never understood the reason for the ratio, it seemed more dogmatic than anything and I'm not sure that I can see where NOT maintaining this ratio has been harmful. There may be other factors obsuring an observation however so I wonder if anyone could clarify the reasons and origin of this ratio and the possible effects of falling outside this boundary. Are there other ratios such as micros that can be ignored or that must be maintained for optimum growth? There seems more to be an effect at threshold levels of individual nutrients rather than at ratios.

Cheers,

 

[Tom Barr]

Re: Required Nutrient Ratios Appear to be a Myth

I agree with this.
There's no good reason for the ratio, although somewhat popularized recently.

The ratio is useful, for not wasting the nutrients and for some that like to mix or use liquid dosing. Doesn't hurt though either.

Regards,
Tom Barr

 

[ervis]

Re: Required Nutrient Ratios Appear to be a Myth

I agree with this.
There's no good reason for the ratio, although somewhat popularized recently.

The ratio is useful, for not wasting the nutrients and for some that like to mix or use liquid dosing. Doesn't hurt though either.

Regards,
Tom Barr

Interesting, but contradictory in itself. It seems the ratio is based upon the plants requirement for each nutrient. If the plants utilized as much N as P as K, there would be no waste of any one nutrient. Simply dump in 1 teaspoon of each, or whatever amount, to maintain greater than zero of all 3. However, when dosed in this fashion, there would be waste? So the ratio is a rough assumption of the plants needs at least.

steve

 

[ceg4048]

Re: Required Nutrient Ratios Appear to be a Myth

Hi Steve,
You raise a good point and I'm sure that the each nutrient is taken up at different rates and quantities but my observations were that under different conditions the fixed ratio was not necessarily valid. I doubt seriously that under all possible combinations of other variables such as light CO2 etc. the uptake of Nitrate is always ten times that of the Phosphate uptake. In some cases where I held NO3 more or less constant but added more PO4 and therefore lowered the ratio I sometimes actually observed higher growth rates. I attributed my varied results to an inability to hold all other variables constant while I varied the PO4. On the other hand at some levels of NO3 I found that increased PO4 had less appreciable impact on growth. (I'll have to confess that many of these "experiments" were accidental where I micalculated the dosage of some component I was adding and I merely observed the results)

In fact I think you can just dump a teaspoon of each nutrient in the tank and as long as each teaspoon provides enough to avoid a deficiency. The Ratio Theory seems to be of the same vintage as the PO4 Limiting Theory so this is another reason I question it. I never actually read notes on any experiments which stated "..NO3/PO4 was held to 10 and growth rates were such and such compared to another tank where the ratio was other than 10 and the growth rates were less.."

I'm not suggesting that as long as each of the NPK are non-zero there should be a one-to-one ratio of their usage, I'm just suggesting that there are instead threshold values for each which maximize growth. If this could be proven, and if we could determine these values then ratios would be one less thing to worry about...

Cheers,

 

[Tom Barr]

Re: Required Nutrient Ratios Appear to be a Myth

That's already been generalized, most of the EI levels target that.
That's why it fixes many of the issues folks have.

It and every method waste some nutrients to some degree, whether there's a ratio like the plants or not, you'll just waste more.

A higher ratio, nutrient level will not cause any harm as far as I've ever seen with all the species I've grown, which is around 300 species.

Some issues in the past have noit been shown to be related to high level of nutrients, but there may be some correlation, yet in the end, most of the time there are other issues that are potentially at play, and when I've gone back and been careful, looking to repeat the effect, the issue disappeared.

So if it was that, I've yet to have seen it, I'm not saying it does not exist, but I also know how to rule it out(or show it's a real effect) if I think it does.

Regards,
Tom Barr

 

[DavidR]

Re: Required Nutrient Ratios Appear to be a Myth

I think that the Redfield Ratio is misunderstood. I don't think it has anything to do with uptake of nutrients, but rather their average existence in plant cells during a period of "balanced growth." Balanced growth refers to "healthy, nutrient replete cells that are growing under steady state conditions." This information comes from a journal artical I have, Balanced Growth in Aquatic Plants: Myth or Reality? by Berman-Frank & Dubinsky.

This would explain why TB's EI method works, and why there is no reason why nutrients must be kept at these ratios in the aquarium. Provide the nutrients and the plants will use them, hence the EI method.

I think the aquarist tries to generalize from the RR that if the molar concentrations are 16:1, then we should supply more N than P, and this is true to some extent, but I don't think it's necessary to keep them at this ratio. Just as long as they are provided.

 

[Gill Man]

Re: Required Nutrient Ratios Appear to be a Myth

This really shouldn't be of any surprise to anyone who has read Tom's writings on EI. It is supposed to be a simple method for getting tanks that have been out of balance, back into a suitable nutrient balance that is beneficial for plants. The next step after plants start thriving and algae starts to disappear, is to fine tune EI to suit your needs and your plants needs, saving the original default EI method, in case problems arise again.

I started fine-tuning EI and dosing by doing 50% water changes every two weeks while still maintaining a 10:1 N to P ratio and ensuring I have enough K, Ca and Mg, dosing 0.2 ppm Fe as CSM+B daily (and ending the week with just 0.1 ppm verified via La Motte test), and dosing 5x the suggested dose of Flourish Excel daily (for now, but will probably back off to 3x after green dot algae is significantly diminished), and maintaining a calculated 50 ppm CO2.

I do this knowing that there is only so far I can go before I start seeing problems and that the point is not to be able to do the least amount of work, but one that I can maintain comfortably, especially when other warm-weather hobbies begin to compete for my time. Am I wasting nutrients? Yes, most likely. Do I care? No. I have THE MOST beatiful plants I've EVER had. A little wastage is worth it. The picture I posted in the gallery a while back is nothing compared to what I have now. It has been utterly amazing, from algae covered plants to algae free plants.

 

[chubasco]

Re: Required Nutrient Ratios Appear to be a Myth

When you have time, how about an updated pic?

Bill

 

[ervis]

Re: Required Nutrient Ratios Appear to be a Myth

Hi Steve,

I'm not suggesting that as long as each of the NPK are non-zero there should be a one-to-one ratio of their usage, I'm just suggesting that there are instead threshold values for each which maximize growth. If this could be proven, and if we could determine these values then ratios would be one less thing to worry about...

Cheers,

I agree totally, and I think the EI method addresses this "fear" in a head on fashion. In fact, taken from the article:

NO3 5-20 ppm
K+ 10-30ppm
P04 0.4-1.5

Isn't this remarkable that the plant bible itself (grin) suggests adding nutrients in the Mytiical Ratio?

I think what we all agree on is this: The ratio is useful only if no one nutrient is in short supply. The ratio is not to be used as a maximum number, but just the opposite, a minimun requirement.

steve

 

[ThomE]

Re: Required Nutrient Ratios Appear to be a Myth

Okay, this is my first post so beat me too much

I understand the 10:1 ratio isn't what reduces algae growth, but as a newbie starting to really understand. It was a security blanket. When I first started, It was really confusing about add this or that.

So, I had my tank at 20 nitr and 2 phos. Of course this didn't hurt my tank, because it made sure that the plants didn't lack anything either. During my one year, I seldom had algae trouble. As I became experienced, I learned that the ratio isn't why I don't have algae (by itself), but because my tank doesn't lack in nutrients. Now when test after water change (old habits die hard), I just make sure I have more than 10 nit and 1 phos. Do I really care by how much? No, it’s to make sure I have enough to start the week.

What am I trying to say? As a newbie, you feel like you have more control when you can test a tank and say 'X' is good number to strive. Instead of just add X amount and you will be good. For me anyway

 

[DavidR]

Re: Required Nutrient Ratios Appear to be a Myth

The 10:1 ratio can be used as a guidline, but I can prove this to be false in a sense. Let's say you have 1ppm NO3 and .1 PO4. How's your tank going to do? Probably not that well, especially if you have high lighting & CO2. It's still a 10:1 ratio isn't it? I'm thinking that it would be difficult to maintain such a ratio.

If you look at is as 10ppm NO3 to 1.0 ppm PO4, then you're better off. But since NO3 & PO4 do not cause algae, what difference does it make if you don't have a 10:1 ratio? As I previously stated (or was trying to infer), plant cells consist of a 10:1 ratio. You can infer from this that plants use nutrients in such a fashion; plants will use more NO3 than PO4, but this is variable from plant to plant, so you don't have to have 10ppm of PO4 in order to grow nice plants. I don't like keeping nutrients in excess, but as long as they are there in adequate quantities, then your plants will do well, and if you are having trouble, then it's another variable that you must look at, like lighting or CO2. Just my 2 cents.

 

[Tom Barr]

Re: Required Nutrient Ratios Appear to be a Myth

I think that the Redfield Ratio is misunderstood. I don't think it has anything to do with uptake of nutrients, but rather their average existence in plant cells during a period of "balanced growth."

No, Redfiled ratio is the average elemental composition of the phytoplankton in the Marine oceans. It is an average based on algae, not SAM's.

Balanced growth refers to "healthy, nutrient replete cells that are growing under steady state conditions." This information comes from a journal artical I have, Balanced Growth in Aquatic Plants: Myth or Reality? by Berman-Frank & Dubinsky.

Do you have a date on this or the journal that it is publiched in?

I think the aquarist tries to generalize from the RR that if the molar concentrations are 16:1, then we should supply more N than P, and this is true to some extent, but I don't think it's necessary to keep them at this ratio. Just as long as they are provided.

Yep,

Regards,
Tom Barr

 

[Tom Barr]

Re: Required Nutrient Ratios Appear to be a Myth

There is the old issue of telling someone so much they get confused.
Then there is the issue of teeling them so much they know you must know what you are talkign about.
Then there are issues with generalizations.

I can tell you to do these levels at ppm ranges with Lamotte test kits of train everyone how to calibrate test kits.

That's a hard sell.

EI is suppose to be simple one stop water changes, dosing , some dosing in the middle to get you through till the next water change. No testing needed to maintain the ppm range you want.

If you are a tweaker, feel free to do so.
I'm not going to encourage testing becasue I know it's not needed and it's simply not going to attrach new folks to this hobby, that is better goal than suggesting testing and micro managing methods that scare people.

Non CO2 methods are simple as well.

I typically suggest these two methods and if folks want more or less growth, adjust the lighting wattage.

That takes care of 99% of folks.

Regards,
Tom Barr

 

[DavidR]

Re: Required Nutrient Ratios Appear to be a Myth

No, Redfiled ratio is the average elemental composition of the phytoplankton in the Marine oceans. It is an average based on algae, not SAM's.

And this differs how? If you could relate this to terrestrial plants as well, it would be great because I'd like to have the greenest lawn in the 'hood!

Do you have a date on this or the journal that it is publiched in?

Yessir! It was published in January 1999 in BioScience, Vol. 49 No. 1.

 

[Tom Barr]

Re: Required Nutrient Ratios Appear to be a Myth

Teh ratio, and this is a general one, there is variation in marine and as well as a SAMs': 10:1 ratio of N to P.

Most of my advice is close to this.
That ratio I found much later.

FW algae is 14:1, again, a general range.

I do not really study terrestials, but my lawn is about 12" deep right now.
You are welcome to come mow it.

Regards,
Tom Barr