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