Adding and measuring K+ - The Planted Tank Forum
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post #1 of 18 (permalink) Old 05-14-2005, 10:06 PM Thread Starter
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Adding and measuring K+

I am using all my ferts and keep all parameters at optimum level except K that is the most difficult to measure.The K added through KNO3 might not be enough and I dont know how much extra K2so4 to add.I started studying the PPS method but i would like to know a rough method of fertilizing until I finish my studies.....

Thanks
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post #2 of 18 (permalink) Old 05-14-2005, 11:11 PM
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I use the Lamotte Potassium Test Kit and I love it, it works great. You have to use distilled or RO/DI water with it though. It also helps to have a bright overhead light and a white surface to hold the test tube over. I ordered mine from Clarkson Lab. No "add to cart," you have to email them, but they will reply and have the kit drop shipped from Lamotte.

I try to keep K levels around 30 ppm. Anywhere from 20-50 if fine IMHO.

Add 0.008436 grams of K2SO4 per gallon to raise K by 1 ppm. For example, for a 30 gallon tank, to raise K by 20 ppm add 5.06 grams K2SO4.
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post #3 of 18 (permalink) Old 05-15-2005, 08:21 PM
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You can easily estimate what your weekly dosing of K+ is.

Then use that with a 50% water change. The K+ level will never build beyond 2x the weekly dose ever(this assumes no uptake by the plants).

If you add KNO3, it's unlikely you need more K+ than is supplied by ther K in the KNO3. You'd need 4x more NO4 relative to K+ before a deficency started.

Test kits are poor at the higher ranges, 10-50ppm. Spectrophotmeters are highly accurate and costly.

A range of K+ is fine, higher levels up to 40-50ppm cause no adverse effects.

If you target 10-20ppm of K+ for weekly dosing(no tank would ever require more than this), then you need not worry.

There is ample K+ for the plants.
Worry about CO2 instead and pruning, aquascaping etc.

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post #4 of 18 (permalink) Old 05-16-2005, 06:23 AM Thread Starter
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Tom you are a life saver,clear,simple ,effective answers.
Thanks a lot
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post #5 of 18 (permalink) Old 05-16-2005, 07:24 PM
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Quote:
Originally Posted by plantbrain
Test kits are poor at the higher ranges, 10-50ppm. Spectrophotmeters are highly accurate and costly.
Have you tried the Lamotte test kit? It works great all the way up to 50 ppm. I have had no difficulty using it and the results match what I would expect based on my dosing. The only spectrophotmeters I've seen just read the same turbid solution that the test kit uses, and are only effective up to 10 ppm. The most accurate way to test would be using an ion selective electrode and meter, but this is very costly and is not just a quick "dip and read" method, test samples must be prepared with ionic strength adjusters first... I think it's easier to just use the test kit.

I haven't read any scientific articles to back this up, but I have read before that high levels of potassium along with high levels of CO2 can cause calcium uptake problems in plants. It would be interesting to run an experiment to test this, if only I had the time!
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post #6 of 18 (permalink) Old 05-17-2005, 09:25 AM Thread Starter
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It would be great if I could use La motte testers but unfortunally in these places are imposible to find
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post #7 of 18 (permalink) Old 05-17-2005, 04:37 PM
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Quote:
Originally Posted by Phil
It would be great if I could use La motte testers but unfortunally in these places are imposible to find
If you're willing to pay for it, these people can get LaMotte test kits to you:

http://www.greenlakes.it

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post #8 of 18 (permalink) Old 05-17-2005, 07:06 PM
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Or you could use the link I posted.
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post #9 of 18 (permalink) Old 05-17-2005, 08:58 PM
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Quote:
Originally Posted by Hypancistrus
I haven't read any scientific articles to back this up, but I have read before that high levels of potassium along with high levels of CO2 can cause calcium uptake problems in plants. It would be interesting to run an experiment to test this, if only I had the time!
I have and it's baloney.
I added K+ to 50ppm and had no response from the plants in question, Ammania gracilus. Erik did the same thing and won at 100ppm the AGA's large contest catagory.He had as his main plant in an 80 gal Ammannia gracilus.
If high K+ causes this, why does it not impact the plant when we added it?

In order for that to be true, we should have been able to repeat the experiement.

I've had high levels of K+ for over a decade. I might know the effects.

We both have low Ca++ levels to boot.

Bark up another tree.

Regarding resolution of the Lamotte test kit.
Can you tell the difference between 22ppm and 27ppm of K+?

If you assume K+ at a high level is an issue, you need to support that contention.

I clearly and resoundly stomped that notion with a simple test to see if K+ was the causative agent.

I've yet to see a single research article in support of K+ blocking Ca++ uptake in aquatic plants at the concentrations in question(say 50ppm or less of K+).

You'll get plenty of hits, but nothing that applies to Ca+ uptake in terms of external plant uptake in the, rather as a secondary messager with stomotal opening which has nothing to do with external nutrient levels and nutrient blocking.

The issue with K+ is one of salinity stress, not blocking of uptake transporters.
Aquatic plants are also surrounded by K+, the studies do not test aquatic plants and K+.

The test I did and many observations over the last decade of widespread K+ use do.

You'll note, I did not answer why someone had issues, I merely answered what it was not!

That is fairly easy to test. You go down, one by one, and remove each possibility and what you are left with often is the cause.

Misapplied references can get you into trouble. The net does not tell you everything and often gives things that are not applicable nor specific to the question/situation at hand.

How you test things and the assumptions you make are key when going through all this.

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post #10 of 18 (permalink) Old 05-17-2005, 09:08 PM
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Quote:
Originally Posted by plantbrain
I have and it's baloney.
I added K+ to 50ppm and had no response fronm the plants in question, Ammania gracilus. Erik did the same thing and won at 100ppm the AGA's large contest catagory.
Man I wish I had where I first read this... anyway, from what I remember, it's when K levels are REALLY high, like several hundred ppm.



Quote:
Regarding resolution of the Lamotte test kit.
Can you tell the difference between 22ppm and 27ppm of K+?
For me, actually, yes! The turbid solution is diluted with either distilled or RO water. Then you insert a tube with a black dot and a hole on the bottom down into the wider tube containing the turbid solution. You just look down through the top, and stop sliding the tube down when the black dot disappears (is no longer visible through the solution's turbidity or "cloudiness.") It will usually end up close to say 20 or 30, or it will end up in between them. So you can tell if it's 20, 30, etc., or somewhere in between. Obviously if the black dot disappears immediately, you have more than 50 ppm, and if you can still see the black dot all the way down to the bottom, you have less than 6 ppm. The key is you need a nice bright overhead light, and a bright white surface to hold the tube over. It really works!
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post #11 of 18 (permalink) Old 05-17-2005, 10:38 PM
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Quote:
Originally Posted by Phil
I am using all my ferts and keep all parameters at optimum level except K that is the most difficult to measure.The K added through KNO3 might not be enough and I dont know how much extra K2so4 to add.I started studying the PPS method but i would like to know a rough method of fertilizing until I finish my studies.....

Thanks
Here is an old post of mine discussing plant needs relative to KNO3 dosing:

This is a repost of mine:

If you dose a fair amount of NO3 via KNO3, keep nice tank parameters, don't have much fish load, I'd suspect you don't need to add K separately.
Steve and I did this for awhile, there were times when folks could not get any K2SO4 around the area, so we did without.

We never really found much difference.Steve suggested we did not need any extra K as it was being supplied via KNO3.

If you have 6.4 ppm of so of NO3, then you add 4 ppm of K using KNO3. Some products have K+, like TMG.
I find it unlikely you really need MORE K+ to grow plants well and ************it's one less thing that folks need to dose which is my goal here****.
Looking at a mass balance of N/K+ ratios, __most/many__ plants have about 1.5 :1 ratios of N:K(Epstien 1972).

Now take into account the O3 part of NO3 and to get elemental N and you suddenly find you have plenty of K+ for plant growth.
So 1.5/4.4= .34 N's for every K+ you add.

So you should theoretically have 3x as much K as you need relative to N x the 1.5/1 ratio = 4.5x as much K+ relative to N per dose.
.
There are other sources of N, plant decomposition, fish waste but some K+ comes from these pools also.
I really do doubt that adding K2SO4 to such a tank will make any significant difference.

Unlike NO3 and denitrifying bacteria NO3=>N2 gas, there is not much to the K+ cycle except for plant uptake/leaching.

So it certainly is something folks can skip if they add KNO3 as their main source of N.

Now if you have a good fish load, over feed Discus, slow growth/non CO2 etc, adding K+ from KCl/K2SO4 is advisable since you already will have plenty of NO3.

But for many, KNO3 as the source of both N and K should do the trick.

I'd say you simply don't need but 3 things, KH2PO4, KNO3 and traces.
And then the other two parts: Light and CO2.

I'm glad Ghori brought it up as I've not thought about it since I guess 1997 or so. But going through it, it should not be a problem even with all the different plant species needs and possible extra K+ needs a plant might have.

I think it's be EVEN easier for the new folks and us too, to delete one more nutrient from the mix.

That is a GOOD GOAL.

The goal is to reduce down with simpler designs/methods/dosing routines for folks that still work very well.

Importantly:
Just remember if you have NO3 issues from the tap/fish load, you will still find a use for K+ dosing from KCl or K2SO4.

Regards,
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post #12 of 18 (permalink) Old 05-17-2005, 10:40 PM
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Not all plants will use the same N:K+ ratio.
Unless your tank recieves at least 50% of the N from fish waste and tap water, it's unlikely you will need to add K in the form of K2SO4/KCL.

Even if the ratio or estimation is off by a factor of 2x, you still are well inside the ball park.

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post #13 of 18 (permalink) Old 05-17-2005, 10:51 PM
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Just a thought:

ADA, Amano's company and Amano himself adds nutrients and then does large weekly water changes(typical 50% weekly).

They do not push and sell test kits/monitoring.
This is not far removed from EI, but is far removed from PPS dosing methods/testing and low frequency water changes.

ADA and myself arrived at a number of things independently as well as others such as Tropica and many hobbyists.

The folks using PPS seem to have a number of algae issues but these are not related so much to the method as to other things like low plant biomass, poor start up procedures and methods etc.

I've done PPS for a month on my 20 gal tank.
Personally, I like the water changes and feel the tank's health and growth is better with the water changes.

Avoiding the water changes allows a build up of organic fractions, testing those is fairly impossible for a hobbyist.

So the PPS introduces many things which you cannot account nor test for.
I do not think they encourage algae, but I do think the plant growth is slowed down some, not a lot, by not doing the water changes.

Anyway, PPS is a method for dosing according to a discussion I had with Edward, not a method for avoiding water changes although some seem to think so.

Water changes work with EI and with PPS as well as the reversed.
Test kits can be used to back up the EI dosing, and after awhile. PPS might not need any testing to dose once you get comfy with your tank.

But learning one vs the other and targettying potential issue and problems is far more difficult with PPS.

But both methods work well IMO/IME.

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post #14 of 18 (permalink) Old 05-17-2005, 10:59 PM
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Quote:
Originally Posted by plantbrain
I have and it's baloney.
I added K+ to 50ppm and had no response from the plants in question, Ammania gracilus. Erik did the same thing and won at 100ppm the AGA's large contest catagory.He had as his main plant in an 80 gal Ammannia gracilus.
If high K+ causes this, why does it not impact the plant when we added it?
Man, I don't know what to make out of my Ammanias then. I had calcium deficiency like curling leaves on both ammania gracilis and senegalensis, and I had PLENTY of every nutrient. As a last resort, I cut back on my K2SO4 dosing two weeks ago, they responded by growing near normal, nice straight leaves. I hope they can continue that way. I might repeat the cycle to see if it is a direct effect. I have to also watch out for K deficiency again. More confused than ever about ammanias.


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post #15 of 18 (permalink) Old 05-18-2005, 10:57 PM
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Quote:
Originally Posted by shalu
Man, I don't know what to make out of my Ammanias then. I had calcium deficiency like curling leaves on both ammania gracilis and senegalensis, and I had PLENTY of every nutrient. As a last resort, I cut back on my K2SO4 dosing two weeks ago, they responded by growing near normal, nice straight leaves. I hope they can continue that way. I might repeat the cycle to see if it is a direct effect. I have to also watch out for K deficiency again. More confused than ever about ammanias.
I've done the test at least 3 times to 50ppm.
I added K2SO4 liberally(as well as KNO3) for years and had very nice stands of A gracilius and Neasea pedicillata.
The stems get about dime size in diameter.

If you add KNO3 liberally as well as CO2, then you don't have so much issue.

Regards,
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