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Why is my PO4 sky high?

Cor

Cor

Member
Joined
3 Nov 2015
Messages
389
Location
The Netherlands
I dose ADA fertz: Special Light, Brighty K and ADA Step-2 for the micro's.
Dosage is daily 2 pumps each, (2ml on 40 liter = recomended)

Testing gives the following results:
Fe - 0.5
NO2 - 0.1
NO3 - 4
PO4 - 5
K - 25
CO2 - 30 ppm
KH - 5.5

(50 liters - Tropica soil powder - good flow and no algea -
Scaper Light 1440 Lumen lights voor 8 hours)

Plant growth is very wealthy but there are some defficiens I think. But as you've noticed the PO4 is way to much?
Leaves are starting to become yellow and the edges of new leaves start to get brown,
the older ones get dark. (those tiny spots is soil/dust - no pins)
Any advice?
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How are you measuring PO4, I hope you are using a proper grade lab kit as hobby kits for PO4 and NO3 are notoriously unreliable. Have you used any dechlorinator recently ?, this can have adverse effects on readings, so can chloride.

If you insist on knowing your PO4 get a kit like this that is not susceptible to interference by other salts.
http://www.lamotte.com/en/aquarium-fish-farming/individual-test-kits/3121-02.html

Anyway high PO4 is a good way of keeping algae at bay. Well done. :D

I ran with 80ppm PO4 for over a week when my dosing pump jammed on. No algae, no fish problems, just a waste of fertiliser really and no change in plant growth.
 
I would be looking more at your NO3 and maybe even iron. Let's say for arguments sake your test kits are right your NO3 looks quite low for a high lit tank which may account for some browning of the edges. If new leaves are yellow could be iron or magnesium if you have soft water. Do you add any magnesium in the way of Epsom salts or similar?
If you say plant growth is good and no alga then whatever the issue is its not major and maybe just needs slight adjustment.
Perhaps the high po4 reading which is probably wrong is down to low no3. Increasing no3 could spur some faster growth and soak up some of that po4 which in any case is about the right ball park for what you want in there.

I would take a closer look at other parameters before worrying about the po4 mate. I know po4 is always the place people start when looking for problems because it's a kicking block but the other ferts are the ones that can cause problems in Plants.
Look at it as no3, mag, traces and pottasium as dinner and po4 as dessert.
If you do have 5ppm in there happy days. Move on to what might not be in there.
 
ian_m said:
How are you measuring PO4, I hope you are using a proper grade lab kit as hobby kits for PO4 and NO3 are notoriously unreliable. Have you used any dechlorinator recently ?, this can have adverse effects on readings, so can chloride.
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I'm messuring with my Sera test box. I've messured 3 times for now and every time the levels are constant.
Don't use dechlorinator, only Green bacter after wc.
 
AverageWhiteBloke said:
Do you add any magnesium in the way of Epsom salts or similar?
I would take a closer look at other parameters before worrying about the po4
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The NO3 is too low, so I will make a extra stock solution to get for example 15ppm?
Don't use any magnesium like Epsom salts. I only use KH2PO4, KNO3, NH4NO3, K2CO3 and MicroMixPlus for the micro's
Meaby the extra NO3 will solve the problem of the browning edges.
 
Cor said:
Don't use any magnesium like Epsom salts
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Why not ?

Mg deficiency can look like Fe or K deficiency.

Epsom salts is very cheap.

It is very unlikely that the is Mg in your tap water, though if you are in the correct part of the work it is possible.
 
Without knowing about your lighting general rule of thumb is to be dosing between 20 and 30ppm kno3 per week.
When I was going through my test kit days I would try and maintain around 20 in the tank regardless of what I was dosing. So if it went lower than that I dosed more. Now I just dose the 30ppm weekly and assume unless the plants are telling me any different it should be enough.
Also look at magnesium though. It's easy to get out of any chemist or health food shop and even adding a little might make a difference if new leaves are yellow.
I think magnesium deficiency is yellow new leaves and Iron is yellow leaves but with green veins. Could be other way round though so confirm that.
 
Cor said:
aren't ppm en mg / l the same?
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For our hobby - yes. I just asked, because some test kits use different units.

AverageWhiteBloke said:
I think magnesium deficiency is yellow new leaves and Iron is yellow leaves but with green veins. Could be other way round though so confirm that.
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I think (not sure) Magnesium deficiency is similar to Iron deficiency, because it inhibits Iron uptake in plants.
 
kadoxu said:
For our hobby - yes. I just asked, because some test kits use different units.


I think (not sure) Magnesium deficiency is similar to Iron deficiency, because it inhibits Iron uptake in plants.
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Excess P can cause issues with Fe uptake too from the charts and articles I have read. They don't necessarily apply to aquatic macrophytes but one would use logic and common sense to start there as a reference point.

I've been experiencing the same problems. I added Ca and Mg. some plants perked up but Hygrophila pinnatifida has developed pin holes on every leaf. Many things at play which would influence nutrient uptake and requirements.
 
Soilwork said:
Excess P can cause issues with Fe uptake too from the charts and articles I have read.
Click to expand...

Could you link these please? Would be interested in reading up on it.
 
AverageWhiteBloke said:
Could you link these please? Would be interested in reading up on it.
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I didn't save them. A simple Google of 'nutrient antagonism' or 'mineral antagonism' will bring up a large amount of fodder. Mulders chart is also interesting.

I would like to hear what others think about this also which is why I started a thread in the water chemistry section titled 'nutrient antagonism'
 
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Hmm, interesting. So now we've all come to terms with which nutrient might be lacking and the symptoms the plants would show there's an extra layer of complication where it might not be too little of something it may be too much of something else and still no accurate way of measuring it. Thanks for ruining my weekend :D

I guess the only real way to approach it would be the likeliness and probability test. So in the case of OP we have....
No Magnesium being added so High probability.
Low NO3 if we believe the test so again high probability.
FE ball park but can't be ruled and could be being inhibited by high PO4 which is a possibility.

In the case of po4 though it's not at any higher values that I guess a lot of people in here are running in their tanks at times dosing 2-3x EI dose. I guess the way to go would be to eliminate all the possibles of not enough then given enough time with no improvement work backwards to see if there could be too much of something.

My gut feeling here though and it is just that, if the OP adds magnesium and a a bit more no3 there might be a bit better growth that will suck up any excess po4 so if excess po4 was limiting fe then that maybe cure both issues?

Po4 is a small relative ppm even at 2-5ppm, simply not dosing it for one week would soon eat that up in a tank with all other nutrients covered and healthy growth.
 
AverageWhiteBloke said:
Hmm, interesting. So now we've all come to terms with which nutrient might be lacking and the symptoms the plants would show there's an extra layer of complication where it might not be too little of something it may be too much of something else and still no accurate way of measuring it. Thanks for ruining my weekend :D

I guess the only real way to approach it would be the likeliness and probability test. So in the case of OP we have....
No Magnesium being added so High probability.
Low NO3 if we believe the test so again high probability.
FE ball park but can't be ruled and could be being inhibited by high PO4 which is a possibility.

In the case of po4 though it's not at any higher values that I guess a lot of people in here are running in their tanks at times dosing 2-3x EI dose. I guess the way to go would be to eliminate all the possibles of not enough then given enough time with no improvement work backwards to see if there could be too much of something.

My gut feeling here though and it is just that, if the OP adds magnesium and a a bit more no3 there might be a bit better growth that will suck up any excess po4 so if excess po4 was limiting fe then that maybe cure both issues?

Po4 is a small relative ppm even at 2-5ppm, simply not dosing it for one week would soon eat that up in a tank with all other nutrients covered and healthy growth.
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Isn't it just wonderful but yes this is of course the problem. Sometimes (eventually) the plants will define the system based on their requirements and uptake rates. Ever had that one plant that just won't grow for you? I'm just playing devils advocate here of course.

I don't think antagonism is a new thing. Hydroponic growers take ratios very seriously or so I'm aware. Soil management. Why can't this apply to plants under water?

Bottom line is I'm no expert and this needs looking in to it at least experimented with.

I think you get the gist. What about high levels of P interfering with Fe and a lack of Fe uptake leading to an accumulation of A N other? Lots to consider.

How do we know the plants chew through the P if it can't be measured accurately? What if adding more P facilitates the uptake rate of something else or antagonises the accumulation of something else ridding the plants and tank of GSA. It would make sense that reducing the original accumulation would also have the same effect. But what is the accumulation?

People care less about K than other nutrients because it is said that it has no effect on fish at high levels but K is a pretty antagonistic nutrient if you look it up. How does this effect other nutrients?

Why did the EI experiment cap at 6WPG of light?
 
Yeah, I think we all have to just take what we know or assume to know and use that as a baseline. Planted aquarium has changed significantly in the last 20 years. There are many things we did then, now known not to have been the case. I guess EI at the moment can be seen as the defacto baseline, one size fits all approach to fertilising plants to adjust from because it has been proved to be beneficial over and over again although I have see many beautiful setups that haven't followed that philosophy. It's never claimed to be the one and only answer more of an idiots guide to growing plants. I guess as time goes on we will further learn about the interactions of these chemicals and the issues they cause when overdosed which is why the hobby is interesting and constantly evolving.

My understanding of the 6WPG cap going off the UKAPS page is that lighting higher than these levels didn't seem to be beneficial to the plants growth or require more ferts than EI was already adding. The assumption is/was that the vast majority of us were never realistically going to try and put that much lighting over an aquarium. I suppose if you just want a planted tank with fish there is going to be a limit to how bright that was before it became something uncomfortable to look at.
 
Yeah well said. I understand the concept of EI. It was a leading question. Why did the plants stop taking nutrients in? Was it really the light that capped untilisation or the amount of ferts that were added?
 
I would imagine the 6wpg cap is because no one is really going to go above theses light levels? Without melting thier plants?
If it was the amount of ferts added the plants wouldnt grow at all regardless of the light levels?
 
Daveslaney said:
would imagine the 6wpg cap is because no one is really going to go above theses light levels
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No it was 6 Watts per gallon was the limiting rate the plants took up nutrients and CO2. Going beyond 6 wpg made no difference as the plants were already running at 100%. :)
 
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