NO3/PO4 ratio (Redfield ratio)

[CT]

Was reading the articles on Redfield ratio. The articles mention about the idea ratio between NO3/PO4 to be 23! so if I am only dosing 5ppm of NO3 and 1ppm of PO4 twice a week as a start, wouldn't I be getting into algae problem(according to the articles, prone to blue-green algae)?

Should I start with a higher NO3 level or lower PO4 level or continue to stick to the original dosing?

[chua]

I am confuse too.

Some recommended a dosing of 5:1 while some say is 20:1.

I know that every tank are different but the great different in the ratio is really strange.

[Sleepy_lancs]

Hmm.. that table is not for dosing my dear friend. That table is used at the end of the week. Say beginning of the week you added 10ppm of NO3 and 2 ppm of PO4. Just before water change, you measure the 2 fertiliser and found that is NO3 = 5ppm and PO4 = 0.2ppm. Then your tank is balanced or so to speak.

[chua]

Thks for the reply sleepylance,

Let me get this right.

So the 5:1 ratio is the recommended dosing and the 20:1 is the balance ratio before weekly water change.

So can i conclude that PO4 is absorbed by the plants at a much faster rate as compare to NO3. The reason is such, since the ratio of PO4 reduces from 5:1 to 20:1 at the end of a week.

[Plantbrain]

Unless part of the ratio is allowed to become limiting, it does not matter.
Plant matter is 10:1 for FW sumbersed aquatic plants. Thjese figures vary widely depending on species, but this is the best general ball park figure.

The Redfield ratio is based on marine algae.

FW algae range in the 14:1 ratio.

But I can have a tank with 20ppm of NO3 and .2ppm of PO4 and be fine.
That's a 100:1, I can have algae or good plant growth in this range.

If I dose a little PO4 each day or I have less lighting, I can maintain the N : P ratio.

Or, I can have 5 ppm of NO3 and 1 to 2 ppm of PO4, this is commonly done over long time speroids.

N : P ratios do not tell what types of N or P, dissolved organics, NH4 vs NO3, these are uptake issues, not just ratios of Dry weight.

If the plants are grown under no limiting conditions, what tyopes of ratios would they have then?

What is an optimal condition? Fastest growth rates? Or moderate growth with excellent red color?

Natural conditions are not always the best conditions and organisms are quite adaptable.

Ratios can be applied to a natural system but aquariums have ther dosing option and the abilty to make the nutrients available even if the ratio is skewed.

You might waste a tad more PO4 or NO3 than you have too, but that's okay, it's cheap.

Regards,
Tom Barr

[Plantbrain]

The other thing, just try it and see if it holds true.
I've kept tanks at ratios far outside these ranges with excellent results.

Everyone said excess PO4 caused algae, but it doesn't.
The ratio does not favor BGA vs plants. BGA need less PO4 and less NO3 to live vs a big old plant.

Regards,
Tom Barr

[CT]

Thus am I right to say as long as the nutrients or always avaliable to the plants, there will be little algae problem?

[PeterGwee]

Generally yes, but make sure the CO2 stays high and good.

Regards
Peter Gwee

[CT]

ok! so CO2 level should be around 20-30ppm

[PeterGwee]

Yes, keep CO2 in the 20-30ppm range but do error on the higher side of things when you have higher light. The other thing to note is to keep the plant mass high whenever possible from the start and do not wait for things to grow in. Keep critter loading on the low side and the critters will thank you for it. They will be of better health and live longer than a crowd tank.

Regards
Peter Gwee

[chua]

So it is not true to say that excess NO3 with cause green algae or excess PO4 will cause BGA as long as the CO2 is between 20-30ppm.

Seem that CO2 is important that need constant monitoring.

Another thing is that for KH of 2, what is the lowest PH it can goes such that the fishes will not be affected?

I had KH =2 and PH =6, according to the Chuck's table, the CO2 level is at 60ppm but my fishes are still swimming and eating normally.
I heard somewhere that better not to have CO2 level above 30ppm to prevent the fishes from CO2 poisoning but why my fishes are not affected?
I am sure i saw some tanks having these parameters as well and their fishes are doing fine too.

[victri]

There are other things in our tanks that will affect PH levels. Some driftwood and rocks can alter the PH of the water, so the chart is best used as a rough estimate.

[Plantbrain]

Decor will not affect the tank too much if large weekly water changes are done.

While CO2 is important, the lighting is also important, less light, the lower the NO3/PO4 can be down to a point where there's not enough light to support Photosynthesis.

A similar issue for plant density, plant species etc.

Anubias would be highly tolerant of NO3 limiting vs Micratheum umbrosum for example.

Regards,
Tom Barr

[juggler]

In the Redfield Ratio article, I am actually a little puzzled as to what he refers to by "green algae". Do they mean Green Spot algae types? Or does it also include BBA, Brush Algae which is suppose to be red algae.

[Plantbrain]

Most likey green hair algae, maybe GW and perhaps GS.

GS is easy to get rid of in CO2 enriched tanks: add enough cO2 to start with and then enough N and finally add traces and lots of PO4.

Dosing PO4 can take Green spot away all by itself if you dose the CO2 good and the other nutrients.

These people are applying a marine concept based on Phytoplankton to FW bethic attached or epiphytic periphyton.
These are totally differnt groups and a poor reference to base an argument on.

It's also incorrect in practical terms as I stated prior.

I've seen a few folks post this person's link but I tried to ask them a question or two but there's no link to email them.

The issues are this ratio does not hold true and is too simplistic and not robust enough. There are a few reasons BGA will grow in a planted tank(unlike many references which often do not have plants in shallow warm water lakes, which will be more realitistic to our tanks), lack of NO3 for the plants will provide a good home fpr BGA.

We are way ahead of these guys on BGA and messing with it and how to deal with it. Green algae etc as well. Maybe 6 years ahead or so.

I culture algae and those ranges are not right, I've had them grow well outside those ranges.

Another huge issue is separating NH4 from NO3 forms when discussing nitrogen and also the dissolved inorganic fraction of PO4 and Nitrogen.

These both play enromous roles in our tanks and in the enviroment with respect to many forms of algae.

Overall the article is helpful since it talks about adding some PO4/NO3/K+.
Attention to the macro's are often over looked or viewed as bad things to get rid of.

But there are some grave issues with the conclusions and the concept.

Regards,
Tom Barr