# Extreme PO4 Consumption?



## Malakian (Aug 23, 2014)

I am having some trouble with twisted leafs on my AR, and GSA on some plants and the drift wood. I am dosing dry ferts (CSM+B,KNO3,KH2PO4,MgSO4,CaSO4, and K2SO4) directly to the tank EI method.
Co2 at 50-60ppm (no fish/shrimp/snails. Ph drop from 7.5-5.9. Drop checker yellow.) Aqua soil substrate, 2x54w t5ho at 35-45 par at substrate.

No3: 25ppm
Fe: 1.0ppm
PO4: Trying to keep at 2-3 ppm, but keeps bottoming out.
GH:7
KH:3
PH:5.97 when max co2, 7.23 before the co2 goes back on. Base PH of water after 24hr de-gas 7.49.

Co2 comes in via ceramic diffuser which is then placed directly under a powerhead. There is about 12x turnover, and good circular flow.
Co2 comes on 2 hours before lights on, and off 30 min before lights. BPS way to fast too count. Have a PH controller to check PH, don't use it for controlling Co2 as I have not been able to get stable co2 levels that way (drifting kh)

Yesterday morning I added KH2PO4 until my test read 5ppm (calibrated) and KNO3 to 50ppm (added a little too much, wanted about 30ppm). Measured No3,Fe, abnd PO4 this morning. PO4 0ppm. No3 25ppm.

Can the plants really be using this much PO4? Or does aqua soil absorb/take up PO4 as well?

How much should I keep dosing, seeing i'm having trouble with GSA? Just try to keep it at 2-3ppm with daily dosing maybe, but then I'm afraid the Fe will become unavailable?¨

Bump; May add my plants are growing ridiculously fast and pearling very well. I trimmed my plants, and 5-6 hours later I could barley see where I cut my Heteranthera zosterifolia, new small leafs already. Never had growth like this  Never used aqua soil and Co2 this high either though. It will be a challenge I guess, when I need to dial down the Co2 to about 30-40 ppm for livestock. I am also using 18lbs tank in about a month with current diffusion method, so gets kinda annoying to keep filling the tanks too. Just wanted to make sure the plants got a good start, and try to eliminate the co2 as the problem if things occurred, as it always seems to be the culprit.

Bump 2nd: Come to think off, since my plants are growing so fast, maybe I need to up my micros too? Seeing my AR is getting some twisted leafes (both AR "mini", and AR "Pink"), and 3-4 leafs on a stem or two on my hygrophila siamensis "53B". Not even close to the AR twisting though, which is more or less every stem. Any ideas would be appreciated.


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## lee739 (Oct 12, 2014)

You are well outside the normal envelope I suspect, I run CO2 about 20ppm, with medium lighting 7hr/d, and my NO3 drops by about 2-3ppm/48hr, PO4 about 0.7ppm over same. Not sure how much NO3/PO4 is added by fish feeding though....


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## Malakian (Aug 23, 2014)

Yeah, I guess so. But still the uptakes seem a bit extreme to be just the plants? I was a little fast on the No3 reading, its more like 35-40ppm. So it has decreased 10-15ppm in 24 hours, or probably more since i'm in the middle of the nitrite cycle which is adding some No3 as well. But without dosing it wouldn't go over 10ppm No3, and I've read at Barr Report that some plants really show there full potential at about 30ppm No3. So i'm trying to target that and keep about a 1:10 ratio to PO4.

I'm guessing its the aqua soil though. Since it is high CEC after all. And in the 2 first weeks I had to dose pretty amazing amounts of GH booster and Sodium Bicarbonate to stabilize the KH and GH at where I wanted it. Bumped up the PO4 to 5ppm again, and I'll recheck tomorrow.

Here are some pictures of the tank (sorry for the glare, sunny out today) and a closer shot of the Reineckii, Hygrophila and GSA.


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## Christophe (Oct 23, 2013)

I have a similar setup to you and have noticed the same thing with PO4. I put in 2 ppm every other day to keep the level up. I find that my system is also very consumptive of potassium, pinholes in AR leaves. I find that I don't have a problem maintaining NO3 at 20ppm or so, but PO4 and K are things I have to consistently work at to maintain.


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## roadmaster (Nov 5, 2009)

When you mention nutrient's dosed per EI are you adding the CSM+B on day after Macro nutrient's ?
I ask only because some report that the Iron and phosphate can precipitate out of solution if CSM+B and macro PO4 are mixed together and dosed at same time.
Is said to be why macro-micro package from say Aquariumfertilzer.com does not include PO4.
I do not fully grasp the mechanisim's by which this might happen, but thought I might mention it for consideration.


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## Malakian (Aug 23, 2014)

Yeah, I am aware of that. Thanks for the heads up though. I have been dosing macros and micros every other day until I noticed the GSA and PO4 reaching 0. I have now been dosing PO4 everyday for 3 days, and other macro every other.

I don't know what to make of this. Anyone with new aqua soil experience the same thing?
5ppm PO4 this morning, 1 photoperiod later (9 hours, light go out 30 min before the plants start "closing") 0.5-1ppm PO4.

Seeing the algae seem to still grow I raised the lights another inch (about 4 inch in total now from where I started), and thinking of lowering the photoperiod 1 hour. I have seen increase in growth rate in plants after adding more PO4. AR still twisted new growth.


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## Hoppy (Dec 24, 2005)

I think you are over concerned about dosing phosphates. If you don't have enough in the water, double the amount you dose each time. I routinely double my KH2PO4 dosages from what the EI tables call for, in order to avoid green spot algae on the glass. It works very well for me, and always has. Also, there is no reason to keep any specific ratio between nitrates and phosphates. The ratio that seems to work well is a lot closer to 3-1 nitrates to phosphates than 10-1.

It looks like you may have high light, considering that you are getting a lot of pearling. With high light, and the fast plant growth that causes, you probably do need to increase your dosage of all of the fertilizers. Remember, excess fertilizers, even phosphates, don't cause algae in a planted aquarium.


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## Malakian (Aug 23, 2014)

Hoppy said:


> I think you are over concerned about dosing phosphates. If you don't have enough in the water, double the amount you dose each time. I routinely double my KH2PO4 dosages from what the EI tables call for, in order to avoid green spot algae on the glass. It works very well for me, and always has. Also, there is no reason to keep any specific ratio between nitrates and phosphates. The ratio that seems to work well is a lot closer to 3-1 nitrates to phosphates than 10-1.
> 
> It looks like you may have high light, considering that you are getting a lot of pearling. With high light, and the fast plant growth that causes, you probably do need to increase your dosage of all of the fertilizers. Remember, excess fertilizers, even phosphates, don't cause algae in a planted aquarium.


Thanks Hoppy! I thought Barr mentioned somewhere that phosphate was the only nutrient that would cause algae if abundant? Maybe I miss-read, or not from a trusted source at all just remember wrong, who knows.

I'll continue dosing PO4 until I can get some sort of balance. Or at least make it last until next dosing :hihi: and double everything else. Ill do another PAR reading with my Apogee and see where we are at, I was more aiming for medium light than high. To much trimming :tongue:
So even something like 20ppm PO4 would be ok? 

I know you don't need to follow a ratio for the nutrients, but I just saw that most used about 1:10 ratio PO4/NO3, and I like being exact with the numbers/measurements and all, so just used that as a guideline for PO4 levels so I had something to go from.

We'll Ill be dammned. You know I mentioned the Co2 to always seem to be the culprit? Indirectly it is the problem for me too, even with the high ppm. Hoppy was right of course. Too high light. PAR meter read around 70-80 par at substrate and 250-300 par at surface of water. Ended up raising the lights another 12" before reaching 50-55 par at the substrate and 150-200 at the surface 

Those 2x54w T5HO's with high quality individual reflector sure is some powerful lights.
Now it looks kinda weird with the canopy so high, so I'm wondering of adding some floaters. Does any body have experience with azolla caroliniana? Really like the look of it, but know little about it. Does it grow as good as other floaters, does it get easily tangled in other plants and become a noxious plant in the tank, like riccia?

Bump: Also added PO4 to 8ppm, NO3 at 30ppm, and K to 15ppm. Ill also add a double dose of CSM+B tomorrow.


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## burr740 (Feb 19, 2014)

I find it hard to imagine the level of plant mass you have is consuming that much P (5ppm in 24 hrs). There may be something to the Aquasoil being new (I have no exp using it, so idk). However, I agree with Hoppy about doubling the dose. It works for me too controlling gsa. I keep mine closer to 10 than to 5. If I run it much under 5 gsa starts to appear.

Raising the light is always a good move to arrest algae problems before they get worse. But it doesnt necessarily mean you had to much for the tank - just that you had too much for the current fert/co2 levels...or plant mass. With your level of co2 and available ferts, 80 PAR is more than doable.

I have ridiculous PAR. Substrate level in my 75 gal -











Ive been running that light for about 5 months. It has actually made the tank easier to manage. Plants grow more compact and bushy, rather than racing to the surface. Pruning/shaping has become a lot easier. I only point this out because you said you dont like the canopy being up that high.


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## dzega (Apr 22, 2013)

same problem here. i need to dose massive amounts of po4. and im sure its not plants using it up. 24h after dose i read close to 0. its been absorbed by something. the tank is dirted. what i do is just dose as much as needed(wich is 3xEI i think). ive seen this problem reported on forums by other from time to time but no real explanation.

another weird thing about this tank is its PH is low for given KH. thats why i cant use dropchecker for co2 monitoring


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## Malakian (Aug 23, 2014)

The tank is only been filled about 3 weeks now, so I guess its still settling in. Maybe I can lower the lights some more when I get things in balance. I too have noticed that the plants tend to become more compact and bushy with higher light, but it has always been algae growing to when I've had intense lighting. But seeing the thread about Tom Barr and him measuring ada tanks at 30-40 par at substrate, with still amazing compact, bushy plants. So it should still be doable.

Bump:


dzega said:


> same problem here. i need to dose massive amounts of po4. and im sure its not plants using it up. its been absorbed by something. the tank is dirted. what i do is just dose as much as needed(wich is 3xEI i think). ive seen this problem reported on forums by other from time to time but no real explanation


My guess its the High CEC in the aqua soil. Some nutrients/minerals it readily absorb, some not like No3. So PO4 might very well be one of which it is absorbing. Exactly how the "mechanism" of CEC and chemicals work, I do not know, but this my general understanding of it.


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## Beefy (Mar 6, 2015)

Malakian said:


> So even something like 20ppm PO4 would be ok?


Levels that high will make it very difficult to keep trace metals soluble. Pretty much the inverse of your problem, which is clearly that something is soaking up the phosphates you are adding.

If you do dramatically increase your dosage just to increase phosphates a little, you should keep a very close eye on your levels. You may suddenly hit a point where the phosphate 'sponge' becomes saturated, and phosphate levels explode.


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## Malakian (Aug 23, 2014)

Just wanted to give an update for future problem solvers, and thank you all for the help.

Algae has more or less stopped growing, still there but not seen any new growth. And my cycle is done, so I chucked in 15 amano's yesterday, and will probably add about 30-50 black sakura today (depending on how many I have the patience to catch). They should clean it up in a jiff ^^ Plants are still growing plenty fast for me, and still pearling 
And it seems like the AR's has a lot less twisting, there is still some waving in some leafs, but nowhere near as bad as before.

I'm still doing 2x EI on everything, except i'm not dosing any KNO3 at the moment. NO3 stays at about 20ppm now after the nitrite bacteria caught up and with the lower ligth. And something (probably the ada) is still sucking PO4 like a sponge, 5ppm per day. So I'm going to add about 6ppm PO4 everyday until that stops. And dialed down the Co2 a tad, just for saftey measure on the shrimp. The ph drop is now about 1.3-1.4, instead of 1.5-1.6.

bump: Oh, and added a purigen bag to the filter, not that has anything to do with this. But its a change made none the less.


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## Malakian (Aug 23, 2014)

Beefy said:


> Levels that high will make it very difficult to keep trace metals soluble. Pretty much the inverse of your problem, which is clearly that something is soaking up the phosphates you are adding.
> 
> If you do dramatically increase your dosage just to increase phosphates a little, you should keep a very close eye on your levels. You may suddenly hit a point where the phosphate 'sponge' becomes saturated, and phosphate levels explode.


Thanks for that, not that i'm going that high. Was just curios :hihi: Ill keep an eye out for when it starts stabilizing. I'm not stopping my daily testing until things are settled and I know how much my plants are using of everything and I will dial it in from there, so I'll stay on top of it.


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## Malakian (Aug 23, 2014)

Oh crap. I just remembered, I have montmorillonite clay (and red clay, if that matters) under the substrate. I don't know exactly how it does it, but it has some adsobring/absorbing or ion neutralizing (or something down that street, can't remember exactly  ) cleaning properties. It has probably something to do with this. Added quite a bit too.

How I did not think of that before is beyond me. :O


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## roadmaster (Nov 5, 2009)

Can only say,,the group of folks that get caught up in trying to measure /fiddle with adding only what they think the plant's are actually using (lean dosing), are the same folks that seem to have more than their share of problems with algae and overall plant performance.
EI dosing requires NO testing, just a leap of faith that is more difficult for some.
Folks that run high energy tanks must I feel accept the principal's of EI more quickly lest they find themselves following threads bout algae treatment's,blackout's,spot treating with chemical's rather than observing good growth of plant's.
Once you eliminate nutrient delivery/deficencies,that only leaves lighting and CO2 delivery to worry bout.
Use less light rather than more,and now you are left with only CO2 or lack thereof to hold up growth.
I take comfort that those running high energy tanks sometimes (not always) use 2x suggested EI dose without incurring algae or harming fishes,shrimp's.
Is odd to me and would seem to require considerable testing /adjusting to try and provide only what plant mass is demanding as the plant mass steadily (hopefully)increases.
what may have been plenty a week or two ago,might not be so.
Seem's much easier (did to me), to start with non limiting amount of plant food and slowly work down if you like until you notice poor performance,and then return to previous %.
Not to say that there aren't those who have managed to run lean fertz, and with success,, but maybe so they don't share all the problems they had getting there to that precise number at which their present plant mass/variety performs well enough.


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## Malakian (Aug 23, 2014)

I will still be following the EI approach with unlimited nutrients. I am only saying there is no point in dosing, say 8ppm PO4 per week, if your plants only use 2ppm. But I will always dose over to have some safety margin. And to me this seems more logical than just follow EI. Thats what I started doing, and I ended up with algae. Without testing I wouldn't know that my PO4 was bottoming out. So I had to adjust up this time, not down. Tom Barr says so himself, this is not a method set in stone.

I am all for EI, but I also don't want a lot (emphasis on a lot) of excess of stuff I don't really need.


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## rick dale (Feb 26, 2014)

*phosphates*

Phosphates do not cause algae. If you are low , add more. Chances are , if you have alge , your phosphates need to be bumped up , or it has something to do with your lighting or your co2. Less light is always better than too much light. As Im sure you know , co2 needs to be very stable while your lights are on.. I dont understand why you couldnt stabilize it with your ph controller. Do you have a solenoid on your regulator ?


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## Malakian (Aug 23, 2014)

The problem with stable co2 and ph controller is that my KH was drifting, which means I got less and less co2 in the water as the KH slowly dropped, without constantly resetting the controller for the new KH value and desired Co2 level. Yes, it has a solenoid.

I am now doing just a steady "on" for the full photo period and dial the regulator in for desired PH drop/co2 level. That way im eliminating variables with water parameters such as KH and so on.


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## roadmaster (Nov 5, 2009)

Malakian said:


> I will still be following the EI approach with unlimited nutrients. I am only saying there is no point in dosing, say 8ppm PO4 per week, if your plants only use 2ppm. But I will always dose over to have some safety margin. And to me this seems more logical than just follow EI. Thats what I started doing, and I ended up with algae. Without testing I wouldn't know that my PO4 was bottoming out. So I had to adjust up this time, not down. Tom Barr says so himself, this is not a method set in stone.
> 
> I am all for EI, but I also don't want a lot (emphasis on a lot) of excess of stuff I don't really need.


 Cannot be all for EI unless following EI .Target ranges which were designed while testing under very high light, and CO2 levels that most don't /won't ever see/use .
They kept increasing the light,CO2, nutrient's,until such time as no more improvement in plant health was noted.(no point adding more)
But if you feel as you say " your way seem's more logical" then..
Hard to bottom out of any nutrient with EI dosing considering how the method was arrived at.
For interesting read on the method.. "The estimative index(EI) dosing with dry mineral salt's" www.ukaps.org


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## Malakian (Aug 23, 2014)

roadmaster said:


> Cannot be all for EI unless following EI .Target ranges which were designed while testing under very high light, and CO2 levels that most don't /won't ever see/use .
> They kept increasing the light,CO2, nutrient's,until such time as no more improvement in plant health was noted.(no point adding more)
> But if you feel as you say " your way seem's more logical" then..
> Hard to bottom out of any nutrient with EI dosing considering how the method was arrived at.
> For interesting read on the method.. "The estimative index(EI) dosing with dry mineral salt's" www.ukaps.org


Then you clearly haven't read the entire post. I have and am at the moment dosing 2x EI (in the middle of the petalphile scale). And yes I did very easily bottom out on PO4 on EI. I dose 6ppm PO4 pr day. Thats 5 times the recommended EI dosage, every day instead of every other, so more like 10 times..I am waaay over. Still bottoming out. And again, Tom Barr (the inventor of the EI method, as you probably know) himself has said this is not a method set in stone. You don't have to follow the exact dosing, thats more of a guideline. Even the "Yet another nutrient calculator" on petalphile.com has a EI "scale", which varies. The value it puts out is low EI values. The core of the EI method is non-limiting nutrients (Liebig's Law of the Minimum), which I am providing or at least trying too with heaps of dosing, and that would qualify as EI in my understanding of the EI method. So EI for me = Non-limiting nutrients, either its 2ppm over what the plants use or 20ppm over, its still non-limiting since the plants can't use it up either way. So why put in waaaay more than your tank uses? That just seems like wasting, as it will go down the drain eventually and not into the plants.

bump: And I have read countless hours on the matter from the man himself, on this forum and Barr Report.

bump 2n: oh sorry, I think we may have misunderstood each other, or I not providing enough info/not beeing clear enough. This does not mean I'm going to be, say dosing 4ppm NO3, just because the plants use 2ppm. I am still going to be having the minimum recommended ppm levels of EI. I just don't want to put excessive amounts in.


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## Malakian (Aug 23, 2014)

It seems to have cleared up completely now. The algae that is. There is only a little GSA on some of the lava rocks and a couple of leafs on the H.Siamensis (a lot less than before mind you), the shrimp did a quick meal of all the other algae this far, little more time and trimming and i'm sure it will all be gone soon enough. Twisting of the AR is still on the decline it seems. Thanks again everybody! 

Bump:


roadmaster said:


> Cannot be all for EI unless following EI


Just wanted to add that doesn't really make sense. Its like saying I cant be for gay marriage because i'm not gay..


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## roadmaster (Nov 5, 2009)

If your test kit is telling you that you have no PO4 but you claim to add two to five times suggested EI target for week,then what good is test kit? You know what amount you have added.
As for my comment bout EI and being all in,you either are dosing EI or your not, and using some modified form possibly as result of inaccurate test result's that lead you to believe you need two to five times target range.
Even if substrate was adsorbing the PO4, it's still there for root's.
In any event,I'm glad the problem is fixed or improving.

I agree completely with Dr. Barr's "It ain't carved in stone" approach, but when I consider the five to 6 watt's per gal and CO2,lighting level's, that EI was expierimented with, to arrive at suggested target ranges for nutrient's,surely you can see why many (maybe just me) would have trouble believing a nutrient shortage.
Massive plant mass, Metal halides, could easily produce higher demand for some tanks but most would suffer from CO2 shortage much much more so that nutrient's in that scenario.
Would be curious,, were any other adjustment's made besides increasing the PO4?
I only ask cause some folks may not share that they maybe also reduced lighting,adjusted CO2 up ,in addition to increasing the macro.
Then they and or other's who might be reading along, have no real way of knowing if it was one or more variables that brought the relief.


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## burr740 (Feb 19, 2014)

Amazing what a triple dose of macros will do.


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## Malakian (Aug 23, 2014)

roadmaster said:


> If your test kit is telling you that you have no PO4 but you claim to add two to five times suggested EI target for week,then what good is test kit? You know what amount you have added.
> As for my comment bout EI and being all in,you either are dosing EI or your not, and using some modified form possibly as result of inaccurate test result's that lead you to believe you need two to five times target range.
> Even if substrate was adsorbing the PO4, it's still there for root's.
> In any event,I'm glad the problem is fixed or improving.
> ...


I have also raised the light, and actually lowered the Co2 a bit. But had you read the former posts, you would know that. Yes, I do know how much I add to the tank, but without testing I wouldn't know how much it is "using". So If I somehow came to the conclusion of dosing 5 times the nomal PO4 dose without testing, which is highly unlikely. Would probably try a lot of other stuff before upping the PO4 that much. And I would probably still do it only on macro day. Leading to 0ppm PO4 in the water for a whole 24 hours at least.

If I where to blindly trust the EI, and think deficiencies cant happen when dosing it. I would still be fiddling with the lights and Co2. Unaware that I have no PO4 in the water column. Which has been linked to GSA.
WPG is pretty inaccurate way to measure lights. To many variables, as the efficiencies of each bulb,how old it is etc. Not to mention ballast and reflector efficiency, distance from substrate. I am using PAR, this is not 100% either but a lot more accurate than WPG. And I am at 50-55 PAR, which isn't considered very high. And for the record, i'm under 2 WPG. Plants aren't always the contributing factor to diminishing nutrients, as in my case. Thats what they tested, plant uptake. Not all the other variables that can be found in a aquarium.

How are you sure the PO4 is still available, do you have a source? Because for me, that doesn't seem to be the case. Not that i'm saying that it isn't. I just don't know.



burr740 said:


> Amazing what a triple dose of macros will do.


Indeed!


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## Malakian (Aug 23, 2014)

I came to think of another thing that probably affected the plants and algae. As I said very early in this thread, I dosed a lot of GH salts to stabilize my GH where I wanted it. So with EI approach in mind, not thinking this is not fertilizers per say, but minerals for the water I dosed heavily. The GH, and KH for that matter has fluctuated wildly and fast. What a rookie mistake, and on top not to think of it. I'm so ashamed 
So the twisting was probably not a direct deficiency at all. Sorry roadmaster, I've should of listened to you, I'm just so stubborn I know. But I did still see improved growth when adding more PO4, and will continue with that as previously stated.

So to get a more stable system, I want to add as little as possible when I do WC's. I did a thorough read on my water from the water supplier and it specifies that it has 24ppm Ca and 0.3ppm Mg. So i'm thinking just adding MgSo4 to reach about 4-6ppm ish and leave it be, do nothing to the KH either (Have been raising KH mainly for filter cycling). But this time I will acclimate the tank with 10% WC each day to I get the GH/KH where my tap is (about 3 dKH, 4 dGH). What do you guys think?


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## dzega (Apr 22, 2013)

roadmaster said:


> If your test kit is telling you that you have no PO4 but you claim to add two to five times suggested EI target for week,then what good is test kit? You know what amount you have added.
> As for my comment bout EI and being all in,you either are dosing EI or your not, and using some modified form possibly as result of inaccurate test result's that lead you to believe you need two to five times target range.
> Even if substrate was adsorbing the PO4, it's still there for root's.


i get the feeling you havent fully understood the point of this thread. its not about bad test kits or lack of belief in EI targets. its about something, most probably substrate is sucking tank dry PO4 wise which leads to GSA and most probably poor stem plant growth.
ive been there so i do understand frustration when next day after adding and measuring po4 at 2+ppm you read 0 and struggle with decidion how much to add next day.


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## roadmaster (Nov 5, 2009)

dzega said:


> i get the feeling you havent fully understood the point of this thread. its not about bad test kits or lack of belief in EI targets. its about something, most probably substrate is sucking tank dry PO4 wise which leads to GSA and most probably poor stem plant growth.
> ive been there so i do understand frustration when next day after adding and measuring po4 at 2+ppm you read 0 and struggle with decidion how much to add next day.


 My(precise) point was/is, that without calibrating test kit against known solution,the hobbyist grade test kit's are suspect at best.KNO3,PO4,etc.
Can google "Accuracy of hobbyist grade PO4 test kit for planted aquariums" and find several threads on different forums discussing "Calibration methods" to ensure what you are reading as result's are accurate.
I learned this with KNO3 test in my own tanks.
LaMotte,and or Hach test's are said to be much more accurate.
Let us say however, that substrate is indeed adsorbing the PO4.
How is the PO4 not still available for plant's rooted in substrate?
You would have to remove substrate to remove that which the substrate has adsorbed/absorbed.


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## Malakian (Aug 23, 2014)

roadmaster said:


> How is the PO4 not still available for plant's rooted in substrate?
> You would have to remove substrate to remove that which the substrate has adsorbed/absorbed.


Some reasons come to mind, my chemistry is not good enough to go into this in detail. But i'm pretty sure as with most chemicals, that a reaction can occur that the PO4 binds to something or precipitates out of solution becoming unavailable to plants. Just what happens to Fe and KH2PO4.

You still haven't provided a source for your claims, so how can you be so sure?
You may know a lot more about chemistry than me for all I know, but I'm the kind of person that just can't take your word for it. I need some facts or some kind of proof.

Bump: And I don't know if I already mentioned it, but in my case, I have calibrated reference solutions. And some plants prefer to take nutrients through their leafs instead of roots, so having nothing in the water column wouldn't be ideal.


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## roadmaster (Nov 5, 2009)

Me thinks all of the answers are indeed in previous post's.
New tank around one month old according to what has been posted.
Aquasoil with high CEC - adsorbing nutrient's which seem's to be the norm according to post's by other's here and on other forums.
Started with 70 to 80 PAR and adjusted down to 50-55 PAR = less demand by plant's for CO2
Dialed down CO2 = less demand by plant's for nutrient's.
Two X EI dosing or better = good nutrient availability for plant's + what aquasoil may adsorb..
After some reading on a couple other forums ,it seem's the aquasoil does indeed adsorb nutrients initially according to other's comment's post's.(maybe month or two)
Might would re-visit post # 12 in this thread for other's have experienced similar conditions where too much PO4 could possibly interfere with uptake of micro nutrient's = new problems.
Glad to hear the problem is receding from what to me appear's to be just a couple needed adjustment's to a relatively new tank while striving for some stability.


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## Malakian (Aug 23, 2014)

Thanks for clear input. Yeah, I have been searching around on the PO4 issue and aqua soil found some similar. But no one seemed to have it as extreme as me. I'm linking that to the Mont.clay thats also high CEC probably further adsorbing nutrients. Its starting to stabilize and I'm down to dosing 6ppm PO4 every other day now, and still have 1-2 ppm PO4 in the water on next dosing day.

As far as I understand the relationship between PO4/Fe is that it isn't a problem before you reach really high PO4 10-15ppm+. You can also overdose micros (Fe) leading to a potassium lock-out if I remember correctly. And the lock-out part does apply to most nutrients, though some need ridiculously high amount before interfering with others.

As far as algae goes, seems like the GSA has almost completely disappeared, so has the twisting. My AR "pink" have never looked this good except from emersed, AR "mini" still a little bit wavy. Now some GDA and some kind of Cladophora seems to be appearing. The GDA mainly on the glass, no big problem but a pain to clean the glass often and throughly. Cladophora seem to barley be making it, growing very slow. So i'm guessing that won't be a problem as soon as I get some fish in there, or the shrimp run out of the diatoms on the driftwood. Haha, "Good guy diatoms" grows where I can barley notice it. So I'm going to do some research on the GDA, as far as I can tell no one really knows the main reason it shows up. Common on new tanks, and Barr's approach is to wait it out.


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## Nazdaq (Mar 25, 2015)

DId you find the cause of the low PO4 levels? I might have a similar problem but i currently don't have any way to meassure PO4 levels so i'm dosing blindly. But i have noticed that the plants only pearl on the days i add KH2PO4 solution leading me to believe that there is a deficiency of PO4.


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## Malakian (Aug 23, 2014)

What substrate do you have? Ada aqua soil will adsorb PO4 for a while when its new, because of its high CEC. I also added quite a bit of montmorillonite clay which is also high CEC, which I believe was the cause for the extreme adsorbing I had.


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## Nazdaq (Mar 25, 2015)

Could it be that im using ECS substrate? i have two different kinds of substrate. First i have 5l or so of ECS substrate in the bottom, here is a link:
http://www.pwss.se/product.php?productid=16172&cat=1928&page=1
Then i have 5-6l of black regular substrate on top. It says on the link that the ECS can absorb nutrients so maybe that's why.


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## dzega (Apr 22, 2013)

my main tank did absorb po4 at high rates for at least 6months. 
it has dirt+ JBL florapol wich is basically clay i think (https://www.jbl.de/en/aquatics-freshwater-products/detail/2347/jbl-florapol)
wich makes sense blaming on the substrate CEC properties


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## Nazdaq (Mar 25, 2015)

Did you remove it dzega?


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## dzega (Apr 22, 2013)

Nazdaq said:


> Did you remove it dzega?


no, i had nice DHG belem carpet all over it at the time i realized it 
i just dosed(and still do) po4 according to actual tank consumption rather than EI dose. for all other nutrients besides po4 i do use EI recomendations.


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## Malakian (Aug 23, 2014)

dzega said:


> no, i had nice DHG belem carpet all over it at the time i realized it
> i just dosed(and still do) po4 according to actual tank consumption rather than EI dose. for all other nutrients besides po4 i do use EI recomendations.


Good to know, seems my assumption is correct then. And I'm doing the same as you, dosing PO4 to tank consumption instead of EI


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## Andy0x1 (Mar 4, 2016)

4 years later - Did your PO4 consumption issue ever go away?

I have been experiencing the exact same problem for 2+ years now. (Deep bed of Fluval Stratum substrate)

I can dose PO4 to 10ppm, it will test dark blue on the test, then 24hrs later it's roughly 0ppm. I went 6 month of overdosing it thinking it would eventually 'saturate' but it never did.


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