Calculation of PO4 I don't follow, can anybody explain?

I think you may want to see what is in the tap water you muse first.
Many folks there have higher PO4 and NO3 in the tap water.

So you may want to account for that.
Generally, algae is due to poor dosing and mostly CO2 issues.

I'd not worry about the PO4 going too high, I honestly do not know what too high might be. It's not toxic to fish and does not induce algae.

However, when you do water changes, this will lower the PO4 down.
So will active strong plant growth.

EI is a starting point for non limiting dosing of nutrients.
It does not imply the CO2 is a factor, so that must be non limiting for the light intensity.

You can reduce or remove KH2PO4 dosing to reduce the PO4 level if you wish.
Or you might reduce the KNO3 dosing to reduce the NO3.
Really up to you, it's a choice based on your own needs and tank.

If you dose 6ppm per week of PO4, the maximum possible build up will be 12ppm if no PO4 is used and you do 50% weekly water changes with tap that has 0.00ppm of PO4.

mg/L = ppm.

A 1/16 teaspoon only weighs .3 grams ,so 3x a week would = .9 grams.
1 teaspoon weights about 4.8 grams for KH2PO4, not 6.
At least the KH2PO4 I use.

Chuck's cal also states the weight at 4.8 grams per teaspoon for KH2PO4.
This means about 7.5 ppm per week of PO4. This assumes no uptake etc and no precipitation.

Differentiating smaller amount of KH2PO4, 0.3 grams is not much or 1/16th of a teaspoon, you have a lot of user error.

If you want more accuracy, you can make a dosing solution and dose that way, however, this method works fine using dry dosing as well.

Even if you have a bit rich PO4, the KNO3 dosing is generally what most focus on modifying.

Regards,
Tom Barr

 

Redfield ratio is 1:10 in terms of MASS of PO4 and NO3.
RR is an atomic ratio, atoms, nothing to do with weights of the nutrients!

Folks have misapplied RR for about 20 years in the hobby..........

there is a web site in Dutch that is popular, and unfortunately very wrong that is promoting this RR ratio idea.

While well meaning, it's simply put: wrong.

Adding enough PO4 and NO3 to be non limiting is the key, and adding some PO4 does help vs none at all.

So you are better off than some past advice, but it's still wrong.

Take atoms and weight their individual weights.

1 P and 16 N's, note, RR does not address weight.

P= 30.97 g/mol
N= 14 g/mol

30.97/14 = 2.2 x error in adding too little

Converting to weight

16/2.2=

1: 7.3 P:N.

Converting to PO4 and NO3, about 1:10.

So 2 ppm and 20 ppm is not a bad target.
I'd still rather have more PO4 than NO3, as most keep tabs on NO3, not PO4 or K etc.

As long as you dose excess P and K, etc, CO2, then NO3 is all that's really left.


Regards,
Tom Barr

 

Here's a little History:

I told Charles the problem with his interpretation of the RR some years ago, but it was ignored and he never emailed me back

Oh well.

If you mess up or make a mistake, you really should admit it, we are all human and we make mistakes and poor assumptions. However, you should try and learn from the mistakes and help other folks not make these same mistakes.

That's why I find it disturbing when folks promote their mistakes on the web and then you have not one person making a bad assumption, you have 1000!

Free of algae with Redfield Ratio | Aquariumpagina's van Charles Buddendorf
No controls where ever used to induce algae in the log growth phase.
You cannot test and experiment with algae unless you do this.

You can say the tank looks nice, you can say you are happy, but you cannot say anything about algae or cause.

Fe dosing is problematic.
Correlating dose in the water to plant growth is not easy.

I've done this type of measurements at the lab.
We use dry weight comparisons and then measure the amount of Fe inside the plant tissues.

The amount of Fe taken in by Hydrilla for example showed the optimal level using Fe with ETDA was about 6ppm!

Very high.

They keep taking in more Fe even up to 8ppm, but 6 ppm have optimal growth rates.

However for our tanks, using Tropica's trace element mix, I feel 5mls per 80 liters 3-4x a week should be plenty. A standard CMS mix is 1 table spoon to 500mls of DI water and add about 15 mls of this per week to an 80 liter tank.

Note: CMS is richer and has more Fe.

However, a fair amount of the Fe we add often never makes it into the plant tissue.

So much of it ends up in the sediment and hopefully the roots will use it if there is no source of Fe in the sediment already.

What happens many times when people believe that limiting nutrients = less algae:

If you limit PO4 severely, this can reduce the CO2 demand to the pouint that PO4 limitation is more significant than CO2. So the plant does not need as much CO2 and adding CO2 is not an issue under these conditions.

When you add PO4, and it is no longer limiting, then your CO2 demand goes way up.

If you did not account for CO2 prior, this would lead you to assume that excess PO4 = algae, if the tank has plenty of nutrients and good light, but no CO2, you will get algae rather fast!!!

Unless you set up the test to account for both sets of conditions and with a tank that is already stable, then you have not done your homework and you have no control.

You also have not accounted for CO2 limitation under high PO4.

Aquarist made this exact same assumption back in the mid 1990's here in the USA.
See here:

Control of Algae in Planted Aquaria

I told Paul Sears, (he has a PhD in Organic chemistry and is a really wise and smart guy BTW!!! I learned a lot from him) that if PO4 was limiting algae, why is it that I had none, and had excellent plant growth?

Essentially I falsified his hypothesis by proving not what causes algae, rather what does not cause algae.

You have to check each claim you make and see and test that. If one of them turns out to be false, you have to go back and figure out what you may have done wrong.

Other folks added PO4, no one was getting algae. We added more CO2 and nutrients and still no algae.

NH4 and high fish loads can produce algae however.
But not NO3 from KNO3 or PO4 from KH2PO4.

These are testable and you can set up a test to prove this to yourself.

Then you ask the folks that believe and claim that limiting PO4 or NO3 limits algae and ask them if that is true, then where is your algae?

It places them in a contradiction.

Unlike Charles, Paul quickly realized the type of error they where making and corrected/admitted it.

Regards,
Tom Barr

 

Rather than trying to specifically isolate individual nutrient issues, it is different for every plant species, it's better to focus on good general care and non limiting nutrients.

Then you are not guessing.

That's fine if someone can hit a good range with their system, but they need to know why it works, not just how, because many other folks can try it and fail.

You need to be able to explain for the most part, why it works so others can replicate the test, methods etc.

I think if you use EI, you can work backwards and assume dosing that much nutrients, you do not need to worry about limiting nutrients.
You are adding everything you need to a level that's non limiting.

This is a pretty safe assumption.

So, you go to lighting.
If you have roughly 0.5 w/liter, then you are most likely in a good range, if you have 2x this amount, that's fine as well.

What is left?

CO2 and current, filtration, routine mainteance, algae eaters etc.

But as far as nutrients, CO2 is the most critical.
Many do quite well without CO2 also.
No water changes.
No dosing.

The trade off?
Growth is reduced 10-20X slower.
so the rates you need to add fertilizer can be met solely from fish waste or perhaps you added soil to the bottom of the substrate.

Non stable CO2 gets many folks into a lot of trouble and then they chase nutrients around thinking they are the cause of all their algae.

Many seem not to be able to test CO2 very well, this issue is hobby wide.
The folks who tend to be good growers also rarely test, they watch their plants and add CO2 more by eye than by a test method.

I suggest using both methods, both the sediment and the water column for getting optimal nutrients and growth.

The ADA aqua soil works really well and it is easy to work with(better than sand + soil etc).

Then you do about 1/2 EI dosing for the KNO3, KH2PO4 and full for the GH booster and the Trace mix.

This works really well.

EI is just a starting point, you can and should tailor the method to your tap and your tank. Eye balling the and simply watching will tell you a lot. If your tank pearling really well after a water change, but rarely for the rest of the week, check the CO2.

Clean filters often, most of these things are common sense but many are way too strict and just take some of the advice and forget the rest.

Regards,
Tom Barr

 

Well, it's a nice diagram, however, i do not agree with nearly 1/2 of it, and I think while a nice looking model, much about what is said is simpkly not correct and speculation at best and worse, just plain wrong.

I have done more than ample investigation inot each nutrient s as it pertains to aquatic plants, not terrestrial plants, not just what I think, rather, what research has been done under controlled conditions.

99.9% of aquarist do not have controlled conditions and cannot isolate nor tell heads from tails about what they are seeing.

Simply measuring light or CO2 is is woefully inadequate.
Not calibrating test kits each time they are used, many issues.
Some of the observations on the diagram I know are not true as well.

If you take a much more conservative approach to assumptions, many of the comments would need revision.

And then how on earth could a planted aquarist get any use out of this monstrous diagram? Could they find specific issues?

Perhaps.
There are too many overlapping interactions to make things significant.
there are way too many species of plants that have very different expession under the same nutrient level.
There are too many issues with light, current, CO2 that influence the plants far more significantly.

I think it's much much wiser to work with a step wise process to see what the problem/s is/are.

Fix one thing and make sure it's fixed and the assumption is safe.
Then move on to the next thing.

Big super charts are good for looking at global relationships, eg gene families, but they just scare most aquarist folks and lead them to be as uncertain as they where to start with.

Thanks for posting!
No need with low light.

I used high light to ask some questions and so I did not have to wait as long or have other factors play a role when looking at plant growth, things happen faster with more light.

At lower light, you are much safer.
I do not use high light because it is "better"
I just want to see effects in 2-3 weeks, not 2-3 months

Yes, the RR allows folks to dose some PO4 so that it does not get too low.
And it keeps the nutrients from bottoming out of going too low.

There is a very wide range plants adapt to, and we see this in natural system as well as aquariums.

So the question becomes, what is the method that gives you the optimal set of conditions for your goal?

Generally: good non limiting nutrients, good ample CO2, low to moderate light.

I think knowing the rates of plant growth that you are use to is very important if you are a gardener. Thus you will resist much change to that.

You know the rates of growth and anything that dramatically changes that, is not a comfortable feeling

But then again, when you can grow any and every plant to high level and quickly, it's nice as well.

So how to control rates of growth?
Light is simply the best most stable method.

Example:



Low light.

The nutrients are really pretty rich here.
A lot is in the sediment as ADA aqua soil.

If you added 3x the light, this tank would need more ferts obviously and much harder to maintain.

Many assume they need high light and more is better.
That is unfortunately.

Light and CO2 drive that entire diagram and can dramatically alter everyone of the results.

So the usefulness is really questionable to me.

It's better to know a lot about light and CO2................... then N, P, K...........

Thanks for the input.

Regards,
Tom Barr

 

Well, the calculator does not take into account the NH4 fraction of fertilizer from fish waste. So it generally is bias towards less PO4 as result unless you feed high PO4 foods to your fish.

The overall effects is even less P relative to N.

the algae successional patterns really do not occur in freshwater lakes or streams where there are a higher percentage of aquatic macrophyte biomass.

There is little pattern in relationship to N and P in such tropical and sub tropical lakes and rivers where there are plants.

Several specific studies using hundreds of lakes have shown this.

Here's are some my professors I knew at Florida, which is the top place perhaps in the world to study FW aquatic plants:

Daniel E. Canfield Jr.

Roger W. Bachmann

specific papers:

http://fishweb.ifas.ufl.edu/Faculty%20Pubs/CanfieldPubs/macrophyte.pdf

You will note, that 7:1 Ratio for N and P, not 16:1.

This is really old news.
20 years or more now.
However, aquarist can be very far behind the research and not see it, or know about it.

Give these papers a good read.

They are informative and specific to our case(warm temperatures, lots of plant biomass, wide range of species, tropic levels.nutrient levels) ocean phytoplankton really are not

Regards,
Tom Barr