Re: Calculations for K

[Thomas Barr <tcbiii at earthlink_net>]

I said:
 
> "To a 1000 liter tank add:
> 
> CO2 to 20-30ppm
> KNO3: 1 and 3/4 teaspoon 2x a week
> K2SO4 2 teaspoons once a week
> KH2PO4 1/8 teaspoon 2x a week
> Traces, your going to hate this: 40mls 2-3x a week.
> Weekly 50% water change."

Neal said:
 
> Now I read this and thought that the K looked kinda
> light in these dosages.   So I ran them through Chuck
> Gadd's dosage calculator (Thanks again, Chuck, great
> tool!).  I did this by setting the tank size to 1000L
> and the amount of water to mix with to 1 ml.  And what
> I found was that these dosage recommendations would
> give you approximately these levels:
> 
> 12 ppm of NO3
> 13 ppm of K
> .84 ppm of P
> 
> Now in reading the APD archives and following a number
> of threads, I thought I had learned that we wanted to
> dose about 5 ppm of NO3 and about 20+ ppm of K over a
> week, if we were to follow the Barr theory of plant
> keeping.  Am I off in my calculations or did Tom typo?
> Or maybe Tom had another reason for loading up on N03
> in this tank?  
> 
> Neal

First off, I'm not shooting for an accurate precise measurement nor running
it through a calculator. I do a rough estimate in my head(which has cobwebs,
rust, some corrosion, and a thick suberized layer+ a lignified secondary
cranium). Same non precise for pH/KH to come up with a CO2 measurement.

I go back and hone things up a bit or let the person tweak it some.
I try and have folks hit a "general" range.

Trying to hit a precise level is simply too inflexible to make into a
generalized rule. Being too rigid has been the problem I believe with some
of the past ideas in keeping plants.

Second off: you might want to consider I said add the KNO3 over the course
of 2x a week, not all at once. That would give 6ppm of NO3, not 12ppm. 6ppm
is not loading up much at all. I get fast NO3 uptake rates and in 3 days,
6ppm will surely be consumed even when my tanks are going "slow".

Now the K+,
From 3.5 teaspoon's of KNO3 and 2 teaspoons of K2SO4.
The total K from KNO3 is about 7.5 ppm.
The total  K+ alone from the K2SO4 is 7.6ppm or so.
15ppm, plus or minus 1ppm is not going to cause any issue for anyone.
But this is based on 2x a week dosing, I do 3x a week on my own tanks which
have higher light etc. Then the K+ is over 20ppm.

If you want a bit more, add another 1/2 or 1 teaspoon of K2SO4.
Don't think you need it. I think in many cases the K from KNO3 is enough,
but it doesn't hurt to have extra it seems.

Seems like plenty of K.

Some traces add it, there is some added from the KH2PO4 also.
20-30ppm is plenty but folks can under shoot it or over shoot by 5-10ppm
with little effect.

When  the plants are growing fairly fast, adding **another dose*** of KNO3
into the mix for a weekly routine ups the K to over 20ppm.

At first, I recommend a bit less than the upper ranges for the NO3. Later,
when the tank is doing good, he can up the frequency of KNO3 and PO4.

.85 ppm of PO4 would be consumed by the tank in less than a week typically.
Another dose would be helpful, but adding this much would remove a great
deal of PO4 stress from the plants. You might get slightly better growth by
adding a touch more etc like adding the KNO3 3x a week by adding this 3x a
week also. That puts in about 1.2ppm of PO4 per week.

If I'm not sure of lighting etc, I'll recommend less KNO3/KH2PO4/Traces.
More lighting, good thick growth of plants, add 3x a week instead of 2x for
these nutrients. Then you get up into the "ranges".

Don't read _too much_ into these levels. They are meant to be flexible and I
have no certain motive for doing this or that or recommending a little more
or a little less:) Don't read into the meanings behind it:) Often there's
nothing there.

Regards, 

Tom Barr