The Role of Potassium?

[Art]

So potassium. It's a macro element but one I find that many people have trouble understanding what it does and how much to put into your tank. I think there is a general guideline out there that says 30 ppm per week.

Companies like ADA have potassium as a separate bottle to dose separately and more tactically than the general combo of macros and micros. For example, they recommend dosing more after a plant trimming.

What say you? How do you add potassium and is more better for plants?

 

[amert]

I got few running with multiple level of potassium.

This one , running with only 5 ~ 7 ppm K on weekly basis



While this one , current setup , running around 20 ppm-ish K i believe more or less ( ignore the orange arrow )

 

[amert]

While this one running with 15-ish ppm K


IMG_20221117_141141

 

[Art]

What is your thinking with the different levels?

 

[GreggZ]

I got few running with multiple level of potassium.

This one , running with only 5 ~ 7 ppm K on weekly basis

View attachment 261

While this one , current setup , running around 20 ppm-ish K i believe more or less ( ignore the orange arrow )



View attachment 262

The talk of potassium aside just wanted to say I LOVE both of these tanks. Very, very well done. You are a serious plant grower Sir!

To me it's no surprise you are running the higher energy tank packed with stems with more K. These conversations always need to be taken in the context of the tank and what's in it.

I remember I got into a conversation one night with some folks on a Malaysian FB group. They gasped when I told them my K dosing. But in general we were keeping very, very different types of tanks. Lower energy tanks = lower demand.

 

[Art]

I agree 100% @GreggZ.

My question, and I don't have a great answer, is whether there is a general target one should shoot for? Where does a beginner start as they have not had a chance to learn the optimal dose for their tank yet?

Also, should you add more after a heavy trimming to help plants recover, as ADA seems to suggest?

 

[GreggZ]

I agree 100% @GreggZ.

My question, and I don't have a great answer, is whether there is a general target one should shoot for? Where does a beginner start as they have not had a chance to learn the optimal dose for their tank yet?

Also, should you add more after a heavy trimming to help plants recover, as ADA seems to suggest?

If taken in the context of a high light stem tank, then a very general rule for me is to have K slightly about NO3. But like many things in this hobby this topic can be hotly debated. Years ago Joe Harvey and I were very interested in some folks who were preaching that keeping K levels very low was the secret to success.

We both set out the same time to test that theory and started gradually lowering K. We both found the lower we went the more many plants rebelled. Now that is only two instances and I am sure you can also find cases of great tanks with very low K. But in our cases it just didn't work. Could there be other contributing factors that we were missing? Of course. And that goes to one of the tricky things in this hobby. Each eco system is unique. And what works in one may not in another. Trial and error is still the only real way to find out what works best in YOUR tank.

As to adding more K after a trimming, I can see how that would be helpful in an ADA type set up as they typically run very lean. In my set up there is never a deficiency of K so likely would have little impact.

 

[Art]

So I asked Tom Barr about his thoughts on Potassium in the aquarium and this is what he told me. I'm posting it here with his permission.

Generally, if you use KNO3 for ferts, you'll never limit the tank via K+. The only way to actually limit K and add the other ferts would to have at least 75% of the N and P coming in from say Fish waste. Like if you had a lot of discus. Or a low light non CO2 set up with soil etc.

NEW ADA soil will have ample N and P, so adding just K+ would do well. 2ppm to 40 ppm for folks really. I've never been able to show any impact from K+ over a wide range going back 25 years. Upper or lower bounds.

The tanks in the garage get nothing and they still do pretty good over long time frames. Has to be low, very low as I do not dose K+.


Recent pic

Plants will vary by species/family perhaps, some are better at low ferts than others. Ammania, Rotala's, Erios and Crypts can put up with some real low levels for ferts generally and the sediment is a big factor also rather than water column ppm's.

The soil in these tanks is about 2 years old now, not new at all. Uptake of K+ in aquatic plants is via the shoots/leaves. Very little comes from the soil.

Plants also have very good enzyme systems that take up a lot when plentiful and use little effort to do so, or very specific low level uptake enzymes that can grab very low ppb's of K+ from the water.

So whatever the ppm/ppb is in the environment, plants will have different affinity systems for uptake. It you bob back and forth with the ppm's, feast and famine...........then it'll cause issues for these uptake systems.

So a low consistent method might work fine, or VERY low consistent system. Or a moderate or a high ppm consistent system.

Slow changes will be okay if the plant has time to adapted, say over 2-4 weeks.

Similar to supply chain disruptions. If things move smoothly, then it works well. Or eating food for humans. If you have a stable balanced supply................ But if you starve too much, or get dehydrated too much, then it'll cause irreparable damage.

 

[amert]

What is your thinking with the different levels?

First of all, i think we need to see this from 2 sides of view as aquascaper.

One with preference in design , another one in plant culture ( plant focused / dutch style / etc ) .

Design is something like what Josh Sim , Yoyo Prayogi , Takayuki Fukada and Matthew Maness doing.

While plant focused is like @GreggZ , Dennis , Raj and Tom doing.

I see there few differences in "setting" for both sides in terms of the layout itself ( before we talk about how these affect K usage )

A. So less shadow area for plant focused scaper layout, but alot shadow on diorama style layout.

We can see almost every plant will get adequate light intensity in plant focused tank ( if not high intensity ).

It's because of the hardscape , the plant arrangement, etc.

B. Diorama / competition tank tend to run with easy plant , like rotala , buce , anubias , monte carlo , hemianthus micranthemoides , fern and so on.

These plants, can even live in low tech with minimal amount of dosing.

Look at Philipe Oliveira , Erkut ( tropic tank ) video and see thier schedule. Philipe running with Seachem, while Erkut using Tropica.

We know how lean these fert are , but thier tank show no sign of serious deficiency except bronzing ( which is for aesthetic purpose ) .

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Because the plant selection itself is on "easy tier " they can hold pretty wide range of K .

Example in my pic, tiger lotus. U see koi / pond people use lotus alot in thier pond. And i bet they never dose any fert ( well , I believe most of them ) but the lotus grow just fine in their setup.

Do u guys ever check local shrimp breeder place? They keep lotsa moss, like christmas moss , java , pelia , even buce in thier setup but nvr dose any fert.

Then u see how betta breeder / guppy breeder in Vietnam or Malaysia or Indonesia, keep their spawn in container / place where they use floater like water lettuce , red root floaters, etc and never dose any.

And their floaters grow just fine.

All the nutrients coming from somewhere else , like from wc , feeding etc.

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Sidenote

@GreggZ I believe not K sir, but phosphorus. Im the one that posted that in Malaysia Aquascaping Club.

And thx to that i learned alot from your dosing.

What i gain now actually thx to your sharing. Thx alot sir

 

[GreggZ]

Sidenote

@GreggZ I believe not K sir, but phosphorus. Im the one that posted that in Malaysia Aquascaping Club.

And thx to that i learned alot from your dosing.

What i gain now actually thx to your sharing. Thx alot sir

That's funny you were there that night. I have to tell you I really enjoyed meeting and interacting with everyone there. It was a real pleasure and very interesting to hear other views of the hobby.

And yes I do remember PO4 was a hot topic. When I posted my numbers they acted like I was from outer space

But like you pointed out very well in your post above, all of these discussions need to be taken in the context of the goals of the tank. ADA type nature scapes have little in common with plant centric "Dutch" inspired scapes.

I've said many times over the years, when you see someone post about how they manage their tank, pay close attention to what's in it. A tank like mine (or yours!) is much different than the other styles like you mentioned above.

And good to see you here my friend. I always enjoy seeing new pics of your tank. It's one of my favorites lately.

Now we need to get your friend Woon Jia to join here!!

 

[JPog]

With all the ADA soil tanks I've setup I usually only dosed K and micros for 6 months without issue. That is pretty much the ADA fert playbook since as mentioned k is not going to be in the aquasoil. I actually haven't even dosed K separately for quite some time, since I always dose on the higher end of EI and it seems that I was getting enough from the KNO3 and KH2PO4.

I agree context is everything, not only with what your growing, but certainly with how much light your using. Since light drives the need for co2 and ferts there is a big difference even what moss, anubias, buce would need if grown at 150 PAR compared to 50 PAR. You would be surprised at how fast some of these "low light" plants grow in high light and they need the nutrients to support it.

 

[plantbrain]

amert's point as far as aquascapers is true, you use tough easy to grow plants, I've not seen difficult species and if so, only very rarely in competitive scaping tanks. Note, some rare or tough to keep plants do quite well at lean ppm's. Absent ppm's, if you use richer soils like ADA AS. Top scapers will redo the entire tank about once every year. So new soil is added. In the mid 1990's, folks go to ferts was K+. People went wild. AGA's contest tank, Erik Leung had over 100 ppm of K+, no ADA soil, just sand or flourite. Big theme of Ammannia gracilus (this giant variety that's orange and weedy).​

​

 

[plantbrain]

As far the biology of K+ in plants, Barko and Smart in the early 198's did several test and radio isotopes to follow where the K+ was taken up and went. In the submersed plants, almost all was taken up from the leaves/shoot, not the roots. It's one of the few. BUT, this was for only a few common weeds, not the 500-800 species or so species. Generally the root systems and the ability to live on very little for the family Lythraceae, Rotalas, Ammannia etc is an exception. They have very strong root systems. BUT we have been using ADA or similar rich clay soils for 2 decades. You put this family in plain sand and super lean ferts, good luck. In ADA soil they need NO ferts, but a rich soil and they do quite well indeed. No, you do NOT need to add careful lean dosing at all. Why folks do that is still somewhat of hobbyist thinking they are doing much more with ferts than the evidence suggest. Hobbyist should try and falsify their assumptions. If you assume they are correct and want to say they are correct, then you NEED to try to falsify them to be sure and advise others. Otherwise you cannot know if what you say is correct, it's wishful thinking and you exposed yourself to having your advice falsified resoundingly. Paul Sears, a PhD in organic Chemistry, he assumed PO4 limited algae. He got that wrong. Spent a lot of time on the topic, gave it a lot of thought. Me? I just falsify and see. Evidence and logic works quite well, but it's not perfect either. Species vary. Perhaps some livestock do not like the levels. Still, for myself, most went after me due to the ppm's being too HIGH, rather than the other direction, not adding any ferts to the water and use the ADA soil. Scrub the water column clean and lock the ferts in to the soil. Plants still have a nice super easy long term source of ferts.

That's pretty easy to do.

Even with stems and 100 umols of light and rich cO2.

K+ is mostly taken up and use as a cation to balance NO3 inside the plant cell's vacuole. So it plays a big role in growth and elongating the cells. It does play a signaling role also, but it's not a function of external ppms or a growth limiting factor etc. It's signaling, not growth or morphology. Folks misapply research in molecular signaling to growth and horticulture. Some basic falsification test show the claim was false. K+ also does not bind to much but clay sheets can contain ample K+ for the plants like Ammannia and Rotala. We could include Buce, Anubias, Crypts, Erios, Snyg's, Cuphea's, UH and UG, Java ferns, most any of the monocot grass like species, actually quite a few species. Micrantheum umbrosum? I always found it a Nitrogen hog. But I could be falsified as I did not test it with ADA AS, just the MC plant. Plants also have several K+ uptake transport systems, called HATS or LATS, high affinity transport systems, or low affinity transporter Systems(and/or a Medium etc). As long as you do not bounce back and forth too much, plants will adapt really well to stable ultra low ppms, or ppb ranges, and then the same plant can adapt to say high 50 ppm ranges also. You can see the enzyme system that controls K+ uptake would be the LATS in the image for say 20-50 ppm. In say my tank with no K+ dosing, the HATS would be the predominate uptake systems. But.....................could that statement be wrong/incorrect? Yes!!! Why?

Where are these uptake systems in the plant? Root hairs? Or the leaves? Or the stem? primary and secondary roots really do not do much uptake, it's those root hairs. The shoot part of the plant likely has them all over. So while no dosing to the water might mean you do not need to dose, there's still a source of K+. And the plant might have a LATS operating in the root hair, and have the HATS operating in the Leaves. People need to think about the whole entire plant and where uptake occurs as well as where the K+ source is. Bacteria in the sediment are also quite plentiful. old leaves, detritus etc, all a huge bacteria factory, and bacteria die, their N, P, K are all lost and taken up in ultra low ppb ranges by those HATS in the roots and/or leaves. Sand it less conducive to this than the clay. Clay, organic matter, and some limy moderate pH all add to CEC also in sediments. Clay mixed with organic peat, or leaves, NH4+ and some CO3 make for a good sediment, pore spaces are large in new ADA soil, as it breaks down over time, the pore spaces are reduced a great deal and there is less O2 for bacteria and the roots. Note, bacteria go after all the carbohydrates leached from aquatic plant roots. Semi reductive mV occur in deep ADA clay sediments also. Messing with the bacteria and root mix in the soil too much, say more than 30-50% at a time, particularly if you do not do a water change soon afterwards, leads to painful results. But most get the idea, big hack and rework, followed by a large water change = good. So K+, PO4, N all are in this same bacterial cycling as well as these different ppm/ppb uptake transporters. You have different species having different optima, KH impacts in the tank water, CO2 is still the biggest rub for folks having trouble and perhaps the higher KH's. K+ is fairly easy and should not be too controversial for most folk's dosing routines. Also, we almost all over dose K+ and have for decades. If you dose any liquid N ferts, or KNO3, KH2PO4, you have plenty, no need for extra. Ratio (atomic) suggest you'd need to get over 75% of the N for plants from biota and fish before you'd possibly start limiting K+.

This should clarify a few things hopefully.

 

[Art]

AGA's contest tank, Erik Leung

That's quite a memory, Tom.

I think this is the tank: Erik Leung AGA 2001 1st Place

 

[Art]

Paul Sears, a PhD in organic Chemistry, he assumed PO4 limited algae. He got that wrong. Spent a lot of time on the topic, gave it a lot of thought.

So for the newer folks that were not exposed to what Tom raised here. Here's is Paul's paper located still on the Krib. I have to give Erik Olson a hug when I see him. This is probably the oldest planted aquarium site on the Internet.

I love being about the same age as Tom. We get to reminisce about things like this and other fun (now seems crazy) stuff like the color of water in a white bucket. Back then, it was all on email!

Oh, and by the way, I'm old. Tom is not. The man is fit like a 20 year old and can probably outrun them still.

 

[Art]

People need to think about the whole entire plant and where uptake occurs as well as where the K+ source is. Bacteria in the sediment are also quite plentiful. old leaves, detritus etc, all a huge bacteria factory, and bacteria die, their N, P, K are all lost and taken up in ultra low ppb ranges by those HATS in the roots and/or leaves. Sand it less conducive to this than the clay. Clay, organic matter, and some limy moderate pH all add to CEC also in sediments.

OK folks. SO much to unpack with Tom's message so forgive me for taking it apart a bit. This up here is fantastic! CEC= cation exchange capacity if you didn't read that before. Really key in a substrate, IMHO.

@plantbrain, would you say that a richer substrate with some of the above qualities would be a better substrate than an inert one with just water column fertilization?

 

[Art]

Messing with the bacteria and root mix in the soil too much, say more than 30-50% at a time, particularly if you do not do a water change soon afterwards, leads to painful results. But most get the idea, big hack and rework, followed by a large water change = good.

Another nugget of good information. I don't think most know this to be true. One of my future questions is about aggressive vacuuming of the substrate with each water change.

 

[JPog]

I'm really anal with any disruption of the substrate. Whenever i move a piece of hardscape or some stems I have 1/2" tubing in my hand and suction out anything followed by a partial water change. Better safe than sorry - preventive measures. Even more so if the tank is plant mass limited.

 

[GreggZ]

I'm really anal with any disruption of the substrate. Whenever i move a piece of hardscape or some stems I have 1/2" tubing in my hand and suction out anything followed by a partial water change. Better safe than sorry - preventive measures. Even more so if the tank is plant mass limited.

Yep substrate and how you take care of it is underdiscussed. It plays a much wider role than most assume.

This goes back to people blaming fert dosing for every problem. If you disturb too much of the soil, particularly without a really large water change, and you can create an ammonia spike. Result? A sudden spike in all manner of algae. Dosing can't fix that.

This is something that people like Marian Sterian talk about a lot and stress. But few listen.

 

[JPog]

Yep substrate and how you take care of it is underdiscussed. It plays a much wider role than most assume.

This goes back to people blaming fert dosing for every problem. If you disturb too much of the soil, particularly without a really large water change, and you can create an ammonia spike. Result? A sudden spike in all manner of algae. Dosing can't fix th
This is something that people like Marian Sterian talk about a lot and stress. But few listen.

I think this also relates to @Art question to @plantbrain about inert vs active. I'll await his full analysis, but generally context is important here I believe. I don't doubt there are benefits to an active soil (lower kh, backup for inadequate column dosing, ammonia?) not that it is an absolute need, but there are benefits. The other factor is many newbies don't know how to handle it or use it correctly. I see so many people who treat it like gravel and their tanks are either extremely cloudy or have green water since they disturbed it (speaking about ADA, can't account for all of them.), and they don't change out enough water.

Because of this, you'll see different results from a tank with the same parameters otherwise. So for some keeping it simple with inert can be a better choice IMO; since we know you can have a successful tank either way.