Low potassium -> high nitrates? - The Planted Tank Forum
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 24 (permalink) Old 03-18-2015, 05:33 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Low potassium -> high nitrates?

I have a hypothesis, and wonder if I might get input as to whether it is on track.

In a relatively large tank (220G) that is low tech but with excel, for the first several months my nitrates were low (5ppm +/-) even after a month or so without water change. Of late, they rise more quickly; I am changing water today and they are probably somewhere between 40 and 80ppm.

The tank is moderately planted (reference shot below), and I think fairly lightly stocked. My goal was to have the plants keep up with the fish, mostly, and do infrequent water changes.

Over the last several months been slowing adding more phosphate to combat some minor GSA. Which seems to be working.

Of late I am starting to see a bit slower growth, and the anubias in particular looked like they are suffering a bit, my guess is potassium (small holes in leaves, browning around holes and tips). Second shot below.

So I started looking into potassium. I have no test kit for it. I use Equilibrium which is very high in Potassium. At the rate I mix (for dGH=6) I should be seeing about 81ppm of Potassium. As I understand it, having about 15ppm is adequate, though high is not an issue.

So here is my hypothesis -- as the tank is maturing, and with infrequent water changes, could I be reaching a point where potassium consumption is outpacing what I am adding with water changes (which are only about 80-90G at a time every 2-6 weeks depending on nitrates), and in turn causing diminished plant growth rates, which in turn means less nitrate uptakes?

Of course there could be a more pedestrian answer, that I'm over-feeding and too much fish poop. But I think I am feeding less now then when nitrates were low.




Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
Sponsored Links
Advertisement
 
post #2 of 24 (permalink) Old 03-18-2015, 06:03 PM
Planted Tank Guru
 
PTrader: (3/100%)
Join Date: Aug 2014
Location: Maryland, USA
Posts: 2,340
Anubias is notorious for liking a lot of potassium around...

As for PPM levels, EI low-light calls for 10ppm as a weekly dose with a 50% weekly water change.. in theory this results in about 20 ppm water concentration. Also, those levels are often insufficient for tanks with mixtures of fast growing plants that consume a lot of K and plants like anubias that want the K levels on the higher end.

Since you're doing infrequent changes, by the end of 6 weeks your 80ppm could easily have been consumed down to a level that would bother anubias.

I'm also guessing that you're not dosing a full 80ppm each water change, just enough to make the replaced water reach 80. Since you're doing about 2/5ths of your water that's about 30ppm you're dosing at w/c.

I'd consider giving it shots of K2SO4 at 5-10ppm on a weekly basis after the first week or two (basically treat the equilibrium as a 1-2 week dose).

New to planted tanks, avid gardener/tinkerer.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Fluval C4 + Quietflow 30, Finnex Planted+ with
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
, low-tech.
10 gallon secondary tank with Finnex stingray with
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
, AC20, low tech
mattinmd is offline  
post #3 of 24 (permalink) Old 03-18-2015, 06:23 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Quote:
Originally Posted by mattinmd View Post
I'd consider giving it shots of K2SO4 at 5-10ppm on a weekly basis after the first week or two (basically treat the equilibrium as a 1-2 week dose).
Thanks, sounds like I am indeed short on K whether or not that is my nitrate issue.

I had at least tentatively added Potassium to my daily dosing. Using a pretty saturated K2SO4/water mix (51gm / 500ml) then adding 30ml daily. I THINK that's going to give me about 1.7ppm per day, about in line with your recommendation.

I had previously been adding effectively nothing (20ml weekly - more or less from Seachem site).

Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
 
post #4 of 24 (permalink) Old 03-18-2015, 07:05 PM
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
It is my understanding that Phosphates play a key role in limiting the balanced growth of plants, and a key ingredient in PMDD etc. to allow low levels of ferts to nourish plants (this all assumes low tech tanks which you have). So it seems that you had a 'balanced' system before increasing phosphates, in that you had growth and nitrates were absorbed by that growth (plus no obvious other deficiencies).
Now you add phosphate, and the fert balance shifts. As zapins has pointed out, and others (plus see Liebig's law), now the limiting phosphate has been removed, and their is a new limiting nutrient - potassium ... maybe more? So your growth stopped (due to limit of K), and nitrates rose again due to lower metabolism?
Could this explain the change? If so dosing to fill to new limiting nutrient seems good, or lower the phosphate back down again (but you need higher levels to combat GSA?).
imcmaster is offline  
post #5 of 24 (permalink) Old 03-18-2015, 07:26 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Quote:
Originally Posted by imcmaster View Post
Now you add phosphate, and the fert balance shifts. As zapins has pointed out, and others (plus see Liebig's law), now the limiting phosphate has been removed, and their is a new limiting nutrient - potassium ... maybe more? So your growth stopped (due to limit of K), and nitrates rose again due to lower metabolism?
Here's the problem I am having with this hypothesis (though it is somewhat mine).

Let's say that I was previously limited by phosphates. by increasing them I may indeed shift to another limiting factor, however.... shouldn't I have shifted at a higher growth rate, and so a higher uptake rate of nitrates?

That's why I am trying to decide the phosphates are not so relevant as that I ran out of something I previously had (Potassium), through progressive reduction as I continued to change water (each change had 80ppm or so, but each change was only 30-40% of the total water)

Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
post #6 of 24 (permalink) Old 03-18-2015, 07:33 PM
Planted Tank Guru
 
Raymond S.'s Avatar
 
PTrader: (6/100%)
Join Date: Dec 2012
Location: Hot Springs Ar. 71901
Posts: 5,935
And the plant @ top center is what type ?

The shortest distance between any two points is a straight line...in the opposite direction...
Raymond S. is offline  
post #7 of 24 (permalink) Old 03-18-2015, 07:42 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Quote:
Originally Posted by Raymond S. View Post
And the plant @ top center is what type ?
Water wisteria.

Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
post #8 of 24 (permalink) Old 03-18-2015, 07:49 PM
Planted Tank Guru
 
PTrader: (538/100%)
Join Date: Jul 2010
Location: Oregon
Posts: 3,009
Unless you are truly trying to figure out why and the process is important to you, why not just supply nutrients at a non-limiting amount(ie estimative index dosing) and take all the guess work out of it. If you continue seeing high nitrates then stop dosing kno3 and up your k2so4 dosing.
nilocg is offline  
post #9 of 24 (permalink) Old 03-18-2015, 07:55 PM
Planted Tank Obsessed
 
imcmaster's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
Posts: 385
Quote:
Originally Posted by Linwood View Post
Here's the problem I am having with this hypothesis (though it is somewhat mine).

Let's say that I was previously limited by phosphates. by increasing them I may indeed shift to another limiting factor, however.... shouldn't I have shifted at a higher growth rate, and so a higher uptake rate of nitrates?
I don't have the knowledge to answer this. But I think the answer lies in the ability of Phosphorus to keep the plant 'stable' and growing without a shift in nutrient need. Keeping a limit on phosphorus levels seems the key in other dosing strategies (other than EI).
imcmaster is offline  
post #10 of 24 (permalink) Old 03-18-2015, 08:22 PM
Planted Tanker
 
burr740's Avatar
 
PTrader: (123/100%)
Join Date: Feb 2014
Location: Bama
Posts: 5,534
Wisteria is a real K hog. Also this -
Quote:
Originally Posted by nilocg View Post
Unless you are truly trying to figure out why and the process is important to you, why not just supply nutrients at a non-limiting amount(ie estimative index dosing) and take all the guess work out of it. If you continue seeing high nitrates then stop dosing kno3 and up your k2so4 dosing.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




burr740 is online now  
post #11 of 24 (permalink) Old 03-18-2015, 08:56 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Quote:
Originally Posted by burr740 View Post
Wisteria is a real K hog. Also this -
Thanks.

Quote:
Originally Posted by nilocg View Post
Unless you are truly trying to figure out why and the process is important to you, why not just supply nutrients at a non-limiting amount(ie estimative index dosing) and take all the guess work out of it. If you continue seeing high nitrates then stop dosing kno3 and up your k2so4 dosing.
I'm definitely still learning and so the knowledge is important to me.

What I'm looking for is a long term balance where the plants and waste offset (mostly) and I can go very long without water changes (a month or more).

As I understand EI, it counts on weekly water changes. I get it, understand that is in some ways better, but ... I don't want to.

I guess (from the little reading I've done) it is more like Tom Barr's "low tech non-co2" method. Except I am adding excel, at least until I get fully grown in. But whatever you call it, and perhaps not for really good reasons (that is what I am trying to understand) I am still trying to get about the "right" amount of nutrients, so as not to be limiting, to err a bit on the high side, but not to build up too much either.

But yes... knowledge is important to me.

Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
post #12 of 24 (permalink) Old 03-18-2015, 09:12 PM
Planted Tanker
 
burr740's Avatar
 
PTrader: (123/100%)
Join Date: Feb 2014
Location: Bama
Posts: 5,534
If the wisteria is healthy, what is most likely happening is the anubias is being out competed for K (or nutrients in general). So you're going to have to reach unlimiting levels globally, in order for the slow growers to have enough left over.

Think of a pack of hungry lions on a fresh kill. The strong are always going to get theirs first. The weak often have to wait for what is left over. So in order for the anubias to eat, so to speak, you need to make sure there's always some left over.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




burr740 is online now  
post #13 of 24 (permalink) Old 03-18-2015, 09:25 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Jun 2014
Location: Cape Coral, Florida
Posts: 1,286
Quote:
Originally Posted by burr740 View Post
If the wisteria is healthy, what is most likely happening is the anubias is being out competed for K (or nutrients in general). So you're going to have to reach unlimiting levels globally, in order for the slow growers to have enough left over.

Think of a pack of hungry lions on a fresh kill. The strong are always going to get theirs first. The weak often have to wait for what is left over. So in order for the anubias to eat, so to speak, you need to make sure there's always some left over.
Yes. Exactly. I just don't want so much left over it creates unhealthy water for the fish, so I'm trying to ease UP to the right amounts, treating deficiencies as I see them.

Maybe that's a bad approach. But so long as the plants look healthy and I get a balance, I do not much care which nutrient is the limiting one, including light. Though I guess light and/or CO2 are the ones that cause the least visible issues with the plants.

Linwood

Latest tank build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Linwood is offline  
post #14 of 24 (permalink) Old 03-18-2015, 09:54 PM
Planted Tank Enthusiast
 
lee739's Avatar
 
PTrader: (0/0%)
Join Date: Oct 2014
Location: Australia
Posts: 532
Quote:
Originally Posted by Linwood View Post
I had at least tentatively added Potassium to my daily dosing. Using a pretty saturated K2SO4/water mix (51gm / 500ml) then adding 30ml daily. I THINK that's going to give me about 1.7ppm per day, about in line with your recommendation.
1.7ppm for that dose in 220g is correct mate....
lee739 is offline  
post #15 of 24 (permalink) Old 03-18-2015, 10:35 PM
Planted Tank Guru
 
PTrader: (84/100%)
Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,015
By far the most important driver of growth rate is the light intensity. You can't use a high light intensity and dose the plants to get low growth rates, without something going wrong. What lighting do you have on the tank?

Hoppy
Hoppy is offline  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome