Adding extra K+ (K2SO4): how much is enough

[growitnow]

Hi,

90gal tank is about 1 month old. My dosing:

KNO3: 8.5g=1.5tsp=15ppm, 3x
KH2PO4: 1.5g=0.3tsp=3ppm, 3x
K2SO4: 10g=1.7tsp=13ppm, 3x
[total K+ being added = 22ppm, 3x]
TPN: 20ml, 3x
GH Booster: 4 tsp, 1x (tap GH=zero)
Ca/Mg: not adding any
Iron: still figuring out how to dose; recently increased to 1.0 ppm, 3x
Excel: dose at 1.5x recommended dose, usually every day
Lighting: 4x55 CF (4hrs 110w + 2hrs 220w + 4hrs 110w)

I noticed small holes in lower leaves of Hygrophila corymbosa angustifolia, typically suggested to be a sign of K+ deficiency. With current dosing, I am adding 22ppm K+, 3x per week (K+ from KNO3 plus K+ from K2SO4).

When I started the tank I decided to dose extra K+ from K2SO4 which is often suggested as unnecessary, just to make sure my EI target K+ would be around 20ppm. With holes in anguistifolia as evidence of K+ deficiency, how much more should I bump K+ up?

Current intention is to change from 10g (1.7tsp) to 20g (3.3tsp) K2SO4, 3x. This change would mean I am adding 35ppm K+, 3x per week (from 8.5g KNO3 plus 20g K2SO4).

thanks,
growitnow

 

[ibanezfrelon]

I always thought i've had potassium deff.. with my hygro polysperma and ludwigia ovalis getting holes..
Now, after adding 60ppm potassium and still some lower leaves getting holes, i'm thinking co2.

 

[Tug]

Not in this case. I'm saying if you have a large source of NH4 and nitric acid then, yes. Large fish mass then start adding 15-20 grams, K2SO4, by all counts. Add .2 tsp KH2PO4, (1/2 teaspoon eod, if you're finding GSA and your working with steady exchange of CO2).

 

[growitnow]

Hi, thanks. Nice of you to reply.

Not in this case. I'm saying if you have a large source of NH4 and nitric acid then, yes. Large fish mass then start adding 15-20 grams, K2SO4, by all counts.

Are you saying, if I have large bioload (lots of fish, large fish), then I should increase my K+ (K2SO4) dosing? But if I do not have a large bioload, then I should not? What is the relationship between bioload and K+?

Add .2 tsp KH2PO4, (1/2 teaspoon eod, if you're finding GSA and your working with steady exchange of CO2).

Sorry for being dense but just to be clear: are you suggesting I also increase my current dosing of KH2PO4 from 0.3tsp=3ppm, to 0.5tsp=4.9ppm, 3x per week?

thanks

 

[Oreo]

I'd like to know the relationship between K & the bioload as well. Good question.

 

[LoudCreature]

to let poor Tug off the hook, you guru class experts ought to know...

http://www.barrreport.com/showthread.php/7404-Calling-Chemistry-and-Math-Pros?p=52131#post52131 pretty well explains.

LC

 

[Tug]

You can increase your K+ even though you already add plenty with the 3x22ppm. Plus you add GH booster. If you have small holes forming on the leaves, it is more likely a CO2 issue.

Same for PO4 and GSA, you could try increasing the PO4 if you see signs of GSA, but CO2 is more likely the issue if you are dosing 3x 3ppm of PO4.

I hope this time the analogy works better.

 

[Tom Barr]

I always thought i've had potassium deff.. with my hygro polysperma and ludwigia ovalis getting holes..
Now, after adding 60ppm potassium and still some lower leaves getting holes, i'm thinking co2.

And you'd be correct

Regards,
Tom Barr

 

[growitnow]

Hi & thank you. Yes that does clarify.

I have been bumping up my CO2. Bubble rate is now over 3bps, I was counting & keeping records of DC color with different bubble rates, etc. I stopped counting when bubble rate became too fast to physically count, and now just observe DC color. Color was previously green and now has become a noticeably lighter green, though not really yellow. DC is low in tank, out of flow of CO2 output. I'll probably keep bumping CO2 up, though cautiously for fish.

I also computed how much K+ was being added from GH booster that I use. Even without changing my K+ dosing, I am currently adding 22ppm K+ 3x per week (as above), in addition to 13ppm 1x per week from the 4tsp of GH booster. Though not entirely accurate 13/3 = 4.3+22= 26ppm of K+, being added 3x per week. That indeed seems like overkill, suggesting CO2 is where to look.

I now understand your (Tug) implication, that an additional sign of CO2 inadequacy might be GSA, if PO4 is at adequate levels and GSA is still present. I have assumed 3ppm P04, 3x per week is a pretty heavy amount that would not likely need increasing.

So what is being suggested is that inadequate CO2 can simulate the signs of K+ deficiency, and can also simulate the signs of PO4 deficiency.

 

[Tug]

I should be clear that I add K2SO4 - I don't add any GH booster. My total K+ dose is less then the amount of NO3 I dose e.g., for every 4.4ppm of NO3, I dose 0.9 ppm of K+ from K2SO4. No holes, knock on wood.

I am currently adding 22ppm K+ 3x per week (as above), in addition to 13ppm 1x per week from the 4tsp of GH booster. Though not entirely accurate 13/3 = 4.3+22= 26ppm of K+, being added 3x per week. That indeed seems like overkill, suggesting CO2 is where to look.

 

[Tom Barr]

Just please adjust CO2 gradually and carefully, watch, wait a a week, then add a tad more.
Do not get impatient. I say this for safety, but also you will learn the subtle differences between the right amount of CO2, adequate, not so equate and poor.
It's not a on/off switch, the range of effects by CO2 enrichment are gradual and continuous.
If you do this too fast, you miss the opportunity to note the range of effects.

This is useful later, when your CO2 drops off a little, or something is slightly wrong, not massive failure etc, or huge algae issues, rather, a nagging so so growth, maybe a touch of algae, here or there etc.
Knowing these more subtle signs is really valuable.

I think you have isolated the 2 issues with algae, ruled out K+, and focus a little more on PO4, but CO2 is still the root issue.
But this is how to best go about a problem, see what you can rule out safety and easily, then focus on what options are left.

CO2 issues get everyone that uses CO2 gas, if not yet, it's only a matter of time. Myself and anyone that's done the hobby, even Amano (ask him sometime) has CO2 issues, he's killed a tank full of fish more than once!!
If it can get myself and Amano? It certainly can get anyone else too. Might get some of you a few times!!




Regards,
Tom Barr

 

[growitnow]

This is rather excellent advice. Because it speaks to how one might approach learning, rather than to simply following a recommendation.

At this stage of my tank and naive 'progression', I have been fighting the urge to throw everything in including the kitchen sink at the first sign of deficiency. The same is true for increasing CO2. The urge may be strong but with excellent advice as this, the force may be with us stronger still. Thanks to kind and knowledgeable folk on this site

Two specific questions:
Can I reasonably assume my K+ (about 26ppm, 3x [includes contribution of GH Booster]) and PO4 (3ppm, 3x) are likely to be nonlimiting, and do not warrant increasing? Or, should I increase either. I don't have a baseline of (my) experience to compare these things to and have selected doses that seemed comparatively high but not over the top. [edit: I do see GSA on lower leaves staurogyne, rocks, and some good on glass]

To observe effect of CO2 increase on pinholes, do those holes on lower/older leaves go away, or should I cut those leaves off and see if new holes develop after raising CO2. Same question for GSA. Does it go away on leaves already affected (e.g., after increasing CO2), or is evidence of a fix that new leaves don't get it.

 

[scottward]

Can I reasonably assume my K+ (about 26ppm, 3x [includes contribution of GH Booster]) and PO4 (3ppm, 3x) are likely to be nonlimiting, and do not warrant increasing?

Check out the EI dosing for your sized tank. If you dose the recommended amount as per EI, you will never run into limitation even at the highest lighting levels. That's the whole point of EI (I think??). You're effectively overdosing (within a safety margin) - so always providing non limiting levels of each nutrient.

I recall reading somewhere that K levels should be adequate simply through the K component of Potasium Nitrate and Mono-Potasium Phosphate if these 2 items are being dosed at full EI level.

I think if you dose at full EI level whilst you are experiencing the problem, you can easily rule out nutrients and then just focus on CO2.

 

[scottward]

Oh - I think those lower leaves with the holes won't improve. You have to watch the new growth at the tips of the plants. If the new leaves that form are looking good (i.e. no holes, good colouration, no stunted/deformed growth) then you have probably hit the jackpot. I'd leave the plants alone for the moment so as not to disturb the roots until (hopefully) new growth shows you that things are looking good.

 

[ibanezfrelon]

To observe effect of CO2 increase on pinholes, do those holes on lower/older leaves go away, or should I cut those leaves off and see if new holes develop after raising CO2. .

Pinholes are irreversable , you should cut off those leaves to see any new signs of deff..

 

[Tug]

I found this on a post by Mr Barr concerning levels and parameters,

Potassium (K+) is a wonderfully easy nutrient to dose that helps a planted tank use up the NO3/NH4 and the PO4. Adding it is easy and the target range is quite large. There have never been any reports of over dosing that I am aware of using K2SO4, although some have had some issues with KCl and certain fish and shrimps but this is due to the Cl anion perhaps. I add 1/4 teaspoon per 80 liters after a water change only. I also am adding K from the KNO3 which I add 1/4 teaspoon 3x a week. This will give you the range of about 20-30ppm or so of K. Any build up is removed by the weekly water changes.

Based on my profound ability to misinterpret what Tom is saying and my limited experience I would say you have plenty of K+ just from the GH booster you add, but adding 9ppm of K+ w/ addition of K2SO4 after a water change would seam to insure K+ is non-limiting.

The effect K+ has on bioload is K+ helps plants assimilate NO3/NH4 and PO4. I am not well versed in the reasons. It is just something I have always excepted as a recognized relationship.

What is the relationship between bioload and K+?

With a larger bioload there is more NO3/NH4, PO4 and K+ is more likely limiting then the other three. Still, keeping 20 -30 ppm of K+ should prevent that from happening regardless.

 

[Tug]

This is pretty heady stuff, but I found this, if it helps.

I am asking because Tom has mentioned that you actually get plenty of potassium just by dosing KNO3 for nitrate, and that would only be true if the N-P-K ratio was actually for Nitrogen-Phosphorus-Potassium. I just want to make sure I am not under dosing Potassium...

 

[Tom Barr]

I
The effect K+ has on bioload is K+ helps plants assimilate NO3/NH4 and PO4. I am not well versed in the reasons. It is just something I have always excepted as a recognized relationship.With a larger bioload there is more NO3/NH4, PO4 and K+ is more likely limiting then the other three. Still, keeping 20 -30 ppm of K+ should prevent that from happening regardless.

The factor that helps a plant take in anions like NO3/PO4 etc is the electrochemical model.
Think of lots of K+ in the plant's central vacuole. All these +++++'s make it very easy to pull in NO3- and the PO4-3, so all these negatives are pulled in with less energy.

The plant vacuole modifies and responds to nutrient demands, salt stress, and many other issues like this. NO3- and Cl- are the main counter anions and then SO4, PO4 etc.

I'd not worry too much about what ppm's these are OUTSIDE the plant, plants do after all, regulate their internal concetrations of these nutrients. The typical external difference in concentration for Fe is 15 orders of magnitude for Fe in the extremely low soil vs the internal concentration inside the plant cell.

So plants can really regulate things as they see fit and take up some at very low external concentrations levels(mostly PO4 and Fe and a few other trace metals).

Plants cannot run away from a bad spot, so they have to tough it out.
They do not grow as well(lower growth rates), but they do live and survive.
If you compare one nutrient dosing method/ppm/concentration difference with another, growth rates/O2 levels are good metrics, not just this steer manure about " Well my plants grow and look nice". You cannot say much about the differences with general statements like "my plants grow fine".
This offers no comparative reference to tell the difference between your routines/ppms etc.

Some can see the difference and make a general note, say 10-20% faster growth, or 5% more O2 at the same time of day. This is more useful. Hydroponic methods can allow you to measure stem increases, leaf count and these methods can be used to compare growth rates somewhat.

I think if you get 50-75% of your total N from fish, then K2SO4 becomes important.
So a non CO2 system, Excel only, lower light, less % plant coverage with a high bioload etc might be useful.

My tanks are high bioload, they are fed a fair amount, but the K+ has never been an issue for me or my client's. I do not lard on the K+, there's no need with KNO3, KH2PO4, and some GH booster.

Does not hurt larding K+ on however.




Regards,
Tom Barr

 

[barbarossa4122]

to let poor Tug off the hook, you guru class experts ought to know...

http://www.barrreport.com/showthread.php/7404-Calling-Chemistry-and-Math-Pros?p=52131#post52131 pretty well explains.

LC

Hi,

I read that post and Tom suggested:

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.

My NO3 is between 20and 30ppm. Since I want to make sure I dose enough potassium can someone please explain to me Tom's suggestion or how much potassium (ppm) should I have in moderate to high bio load tank. Thanks.

 

[LoudCreature]

Hey Barbarossa4122, what's your game now can anybody play? ...

I was just trying to rescue our poor little Tug.

This may be one of those “context” things, the piece cited is from last millennium, a millennium is thousand years , so a thousand years ago people believed all kinds of things and one of them was we need 3 or 4 times as much K as NO3.

In modern times most people seem to think about the same amount of NO3 as K works. Lucky for us old timey people, extra K doesn't hurt much.

And I think there has been enough discussion of this lately, you ought have realized that

LC