# Having trouble keeping phosphate up



## jsiegmund (11 Mar 2015)

I have a bit of an issue getting the phosphate level in my tank to decent values and I want to understand why. I am using a drop test to monitor the values and although there is sometimes a hint of blue in the water, I can't get it to show a real blue color which it should be. 

This seems to be the case since I switched to Akadama. I read these soils might take up some PO4 in the begin period, but I've got it for several months (4) now, and there's still nothing happening. At the moment, I'm dosing 6 ppm / week and just upped that to nearly 10 just to see what will happen. 

Why change it at all? I think it's whats causing poor plant growth in my tank. Some plant species like pogostemon helferi and bacopa sp japan are struggling. Lower leaves are melting and algae are always present (BBA, hair, green spot). Of course there are other factors like CO2, nutrients and light but I do believe I have those under control, at least well enough. Other plant species are doing better (blyxa, enchinodorus tenellus, eleocharis parvula and others) so that leads me to think that stuff like light and CO2 is at least well enough. 

So if I want to get PO4 up to something like 0.5 or 1, I just keep adding the dose until something happens, or are there other factors to take into account? I'm dosing a PO4 stock solution made with powder from a local supplier, I know pretty sure it's ok. One drop in my test solution and it turns blue almost instantly. 

If it is the Akadama, from what I read the roots of the plants should be able to use still use it. Especially the pogostemon has thick roots which seem to be ankers more than meant for uptake. Could this be why it is doing a bad job taking in PO4? Just trying to find some reasonable explanations here


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## Vivian Andrew (12 Mar 2015)

I never tested for po4 but when it is less your tank will show some sign like GSA in leaf and glass, I added Eichhornia Diversifolia plant last month and start getting GSA Eichhornia Diversifolia leaves also started turning black which is a po4 issue so in my EI dosing i increased po4 within a week all came to normal, i make EI stock solution according to calculator i use my dosing is 1ppm and now i increased to 2ppm below are the sites i used to make my EI stock solution.

http://rota.la/

http://www.theaquatools.com/fertilization-calculator

Pogostemon helferi will melt if your PO4 is high, for lush growth you need to increase nitrogen and water flow and good lighting will keep it compact, and whenever you increase or decrease dosing you need to give a weeks time for seeing the changes.


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## ceg4048 (12 Mar 2015)

jsiegmund said:


> or are there other factors to take into account?


Hello,
       Yes, the other factor is that PO4 test kits cannot actually tell you how much PO4 is in the water. You should stop using test kits to measure nutrient levels and simply dose the required amount. You will save yourself a lot of trouble in the long run and will save money too.

Cheers,


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## roadmaster (12 Mar 2015)

Me think's that if one were to search out PO4 target range with something like EI dosing scheme , which assures non limiting macro/micro nutrient's , That one can fully appreciate what Clive is saying about test kit's.
If target range for particular nutrient was say 1.0 to 2.0 ppm, and my test kit indicated nothing after adding 6 to 10 ppm,then I would question the test kit's result's or the tester.


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## jsiegmund (12 Mar 2015)

ceg4048 said:


> Hello,
> Yes, the other factor is that PO4 test kits cannot actually tell you how much PO4 is in the water. You should stop using test kits to measure nutrient levels and simply dose the required amount. You will save yourself a lot of trouble in the long run and will save money too.



Well before I had my akadama, those same tests worked fine. But fair enough, let's assume they don't. The "required amount" will still very much depend on how much the intake of plants is, correct? And if the soil is also absorbing, that amount would be even higher. So how to I find the required amount then? When I refer to the normal calculators, I'm already dosing too much and I really do not think lowering the dose is going to solve my growth/algae problems. So I'm not using the tests to measure as such but just to get an indication whether there is anything left in the water column.


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## Rahms (12 Mar 2015)

jsiegmund said:


> Well before I had my akadama, those same tests worked fine. But fair enough, let's assume they don't. The "required amount" will still very much depend on how much the intake of plants is, correct? And if the soil is also absorbing, that amount would be even higher. So how to I find the required amount then? When I refer to the normal calculators, I'm already dosing too much and I really do not think lowering the dose is going to solve my growth/algae problems. So I'm not using the tests to measure as such but just to get an indication whether there is anything left in the water column.



look at the EI tutorial.  You dose excess and forget about it! much easier


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## jsiegmund (12 Mar 2015)

Rahms said:


> look at the EI tutorial.  You dose excess and forget about it! much easier


That's the point: I am already doing that. I'm dosing even more than EI prescribes and still have deficiencies. So I tested to find out why and it turned out PO4 in my water column is zero, at least according to the tests.


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## ceg4048 (12 Mar 2015)

jsiegmund said:


> Well before I had my akadama, those same tests worked fine.


Yes, but unfortunately, that was also an illusion. PO4 test kits only ever work as if they were a lottery. Just as frequently, the test kit reads a false high and the hobbyist, being paranoid about PO4 then restricts the dosage level. That's where the trouble starts. The low levels of PO4 causes the plants to suffer and this triggers algal blooms or causes other health issues. The hobbyist then blames the high PO4 reading for their troubles and this sets up a never ending cycle of problems. There is hardly such thing as dosing too much PO4, so straight away we can tell that this is leading down the wrong path.

As mentioned by Rahms and other posters, read the EI Tutorial and dose the amounts shown in the article based on your tank size or use the calculator in the link. Then forget about trying to micromanage the nutrient levels based on measurements.

Cheers,


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## Jose (12 Mar 2015)

If you dont want to listen to ceg jsiegmund, then you have to at the very least calibrate your test kit. You should forget about the test kits imo though. You are obviously being missguided by them at the moment.


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## jsiegmund (12 Mar 2015)

Okay, let's make it clear that I very much appreciate everyones input. Especially Clive's whom I regard as the expert given his track record on these forums. Let's also make it clear that I'm *already dosing by EI. *It's too easy to say all problems will just magically disappear when you just follow EI, that's not true as its success depends on more than just adding the right nutrients. There's flow, CO2, light, well you guys know it.

So whilst dosing via EI (NO3, PO4 and Ferrdrakon for micro's), I am still seeing deficiency problems and algae popping up. So one tries to eliminate probably causes. I have done so for CO2 (yellow drop checker, 1 point drop before lights on). I have done so for flow (upgraded to FX5 with spray bar). I have done so for lighting, etc. etc.

The only option I have got to check if my water column nutrients are ok are these tests. It's not like the plants are going to write my an e-mail to tell me what's wrong. So I have tested to see what the levels were and the PO4 surprised me because I expected it to turn blue which it didn't. So I googled around and found some stuff on Akadama absorbing PO4 which made me wonder whether this could the a problem or not. That was when I posted this question. So it's fine to tell me to dose EI, but perhaps we can focus a bit more on the original question instead.


PS: dosing according to EI would mean I drop my PO4 back to the level I had it on for months (2 ppm). I can do that, but I fail to see why that would suddenly make a difference when nothing else changed.


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## ian_m (12 Mar 2015)

Jose said:


> then you have to at the very least calibrate your test kit


Calibration is irrelevant, you cannot use a hobby test kit to measure PO4 levels in tank water. As Clive has stated there are other substances present in tank water that will cause PO4 test kits to misread, generally grossly under read or read zero, despite PO4 being present. People see this low level from their kit and start chasing and worrying about something that is a non issue.

Overdosing PO4 is not an issue either. After a pump failure and dumping 1litre of double strength EI solution into my tank my PO4 level was 85ppm....nothing happened. No algae, no fish issues and more boringly no change in plants....


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## Jose (12 Mar 2015)

jsiegmund said:


> The only option I have got to check if my water column nutrients are ok are these tests. It's not like the plants are going to write my an e-mail to tell me what's wrong. So I have tested to see what the levels were and the PO4 surprised me because I expected it to turn blue which it didn't. So I googled around and found some stuff on Akadama absorbing PO4 which made me wonder whether this could the a problem or not. That was when I posted this question. So it's fine to tell me to dose EI, but perhaps we can focus a bit more on the original question instead.



If you run a test. If you prepare two solution of say 5 and 10/15 ppm phosphates in RO water and then test it. Your test kit should show two different colours. At least this way we can know your test kit is minmally working (not saying its appropriate). Then you can test your tank water. This way you wont get an exact ppm at all but you can know if you have some or no phosphates in the water. Not that this is gonna be of much help though.


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## ian_m (12 Mar 2015)

Jose said:


> Then you can test your tank water.


Regardless of calibration, it will not read the correct PO4 level, due to other substances present in tank water. My bet is it will read zero....

This had been shown time and time again, dose tank using dry salts to certain ppm level. Wait a while, use hobby test kit to measure level....surprise surprise it doesn't agree with the ppm you have just dosed at...


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## Rahms (12 Mar 2015)

jsiegmund said:


> The only option I have got to check if my water column nutrients are ok are these tests. It's not like the plants are going to write my an e-mail to tell me what's wrong. So I have tested to see what the levels were and the PO4 surprised me because I expected it to turn blue which it didn't. So I googled around and found some stuff on Akadama absorbing PO4 which made me wonder whether this could the a problem or not. That was when I posted this question. So it's fine to tell me to dose EI, but perhaps we can focus a bit more on the original question instead.



I think the problem is that the test kits provide a way of "measuring" nutrients, so you're focusing on that, because you can't measure other stuff (or, you've got a positive result in case of CO2).  You've got a bigger filter- therefore decided flow is solved.  You've got a yellow drop checker- therefore decided CO2 is solved.  Now you've looked at an unreliable test and concluded this is where your problem is, when in reality, having a big filter and a yellow drop checker doesn't mean your flow and CO2 is perfect. Where is the drop checker in your tank? You said its pogostemon helferi and lower parts of bacopa that are struggling- close to the substrate, which is where it's hardest to get good flow/distribution.

Some photos would probably help


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## Jose (12 Mar 2015)

ian_m said:


> Regardless of calibration, it will not read the correct PO4 level, due to other substances present in tank water. My bet is it will read zero....
> This had been shown time and time again, dose tank using dry salts to certain ppm level. Wait a while, use hobby test kit to measure level....surprise surprise it doesn't agree with the ppm you have just dosed at...



If the kit is not able to read phosphates at all then youll find that out when you run the test mentioned before. It definately wont give a ppm, as you state ian m because of so many things but it can give a sense of having some or no phosphates at all if used correctly.


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## jsiegmund (12 Mar 2015)

Rahms said:


> I think the problem is that the test kits provide a way of "measuring" nutrients, so you're focusing on that, because you can't measure other stuff (or, you've got a positive result in case of CO2).  You've got a bigger filter- therefore decided flow is solved.  You've got a yellow drop checker- therefore decided CO2 is solved.  Now you've looked at an unreliable test and concluded this is where your problem is, when in reality, having a big filter and a yellow drop checker doesn't mean your flow and CO2 is perfect. Where is the drop checker in your tank? You said its pogostemon helferi and lower parts of bacopa that are struggling- close to the substrate, which is where it's hardest to get good flow/distribution.
> 
> Some photos would probably help



You're making assumptions here. I am not saying I have CO2 solved; I am saying that based on a yellow drop checker and 1 point drop it is probably safe to say that it's not terrible. Same goes for flow, I'm not saying it's superb but it's not terrible either. The tablets for my corydoras float away when I place them in the area where the pogostemon is. So there definitely is flow.

So let me ask you guys a question. If all of the tests are rubbish and you have a tank running on EI which has some sort of problem, whatever that is. How do you solve it then? Just dose EI some more and wait for it to go away on it's own? I'd say you need to have some way to at least have an indication of something to improve. And when the obvious ones (CO2, flow) are ok, then what? Or do you recon that dosing EI is sufficient to rule out any issues with nutrients / water chemistry? I'm not criticizing here, just want to understand the reasoning.

Photo's:


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## ian_m (12 Mar 2015)

Seeing as EI is about 5-10 x what the plants actually need/use, lack of ferts won't be the issue.

On saying that we have seen people dosing levels that are way way out, in that they mixed their ferts wrong and dosed wrong giving virtually no fertz in the tank.

Also seen people roll their own EI mixes and doses, usually missing the cheapest ingredient, MgSO4 out as they have hard water so must have Mg in it so no need to use MgSO4. Wrong.

So in summary only leaves a CO2 issue or incorrect light levels. "Mechanical" defects in plants usually points to low/incorrect CO2.

Some people have reported some specialist aquatic soils leaching huge amounts of ammonia for the first couple or months, fatal for fish and damaging for plants and filter flora/fauna. Solved by daily water changes and/or use of Amquel+ (or equivalent).


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## Jose (12 Mar 2015)

EI normally does rule out all issues with nutrients yes as long as its done correctly and with all nutrients. That said, there are some cases where something with nutrients might not be right though. Like in your case of a soil adsorbing the nutrients (Im not saying its true but its a possibility), or also the case of very  very hard water (this is another possibility). These cases are quite uncommon, yet CO2 cases are very very common and thats why its so easily misdiagnosed.


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## roadmaster (12 Mar 2015)

If dosing via EI which ensures Non limiting,(key word) and you have a problem, nutrient's or lack thereof are most often not going to be the problem.
This only leaves lighting, CO2 delivery,distribution, and or flow to help get the gas to lower regions for carpet type plants.
The gas want's to leave nearly as fast as it is entering and might very well be why suggestion of moving the drop checker around to different area's as well as   lower,  might be informative.(color may indicate not as much as hoped for nearer the bottom)
Course,,lowering the intensity and duration of the lighting would lower the demand for nutrient's as well as CO2 and this alone might bring relief assuming as you say the CO2 delivery/distribution is adequate.
If I spoon in or squirt in X ppm of a  nutrient as per a dosing scheme, then I know the nutrient is there.
I do not worry bout the uptake rate of the plant's for the amount I added is  non limiting.
If by some mechanisim the substrate adsorbed some as well,then plant root's will utilize it as well.
I can take comfort (trust) that the plant's will not need more for growth until next dose which happens to be in line with weekly water changes that most sign on for when they begin the hobby.

GAHHH! I'm too slow with my fat stubbyfingers to get message out before other's.


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## jsiegmund (12 Mar 2015)

Ok so I will give you a bit more info on what and how I dose and other details.

PO4 and NO3 I buy in powder form from a Dutch guy (I think he's on ukaps as well). It's KNO3 and KH2PO4 in pure form. I'm using RO water to create two stock solutions and use a dosing pump to daily dose the appropriate amount in my tank (happens just before lights on). For the rest of the nutrients, I use Ferrdrakon. Actually just finishing the last of it and then I'm switching to KramerDrak which is supposed to be even a bit better. But still, Ferrdrakon is also perceived as a very good source of nutrients for plants.  That one is dosed after lights off, 6ml / day (= 42ml / week). Recommended is 25ml / week for a tank my size. I must admit that I haven't translated these values to EI and wouldn't exactly know how to do so.

My water change is once a week in the weekends, 40%. I'm using 50/50 tap vs RO, where my tap water is moderate (KH9 / GH7... measured with drop tests....). The akadama lowers the KH to 1, GH is normally around 8 - 9.

I'll move the drop checker closer to the bottom to see whether that matters. 

Ferrdrakon consists of:


> 3,000 mg/l potassium, 1,000 mg/l iron, 750 mg/l magnesium, 400 mg/l manganese, 60 mg/l boron, 20 mg/l copper, 20 mg/l molybdenum, 20 mg/l zinc, 10 mg/l nickel, 10 mg/l cobalt, 4.6 mg/l iodide, EDTA, HEEDTA, DTPA, NTA, methyl paraben, ascorbic acid



Source: http://www.drak.de/en/freshwater/fertilizer/ferrdrakon.html


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## Jose (12 Mar 2015)

So you dont really know how much you are dosing? Or did you make the solutions as per EI instructions/ammounts?
Also if phosphates were low youd most probably see green spot algae. Is this the casE?


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## jsiegmund (12 Mar 2015)

I do know for the macro's. I'm dosing 22.50 ppm NO3 and 2 ppm PO4. The solutions are 1ppm / 100L (NO3) and 0.1 ppm / 100L (PO4) so I've calculated the number of milliliters per day to match the desired dosage in ppm. That's 7 vs 6. For the micro's, I'm doing almost double the recommended dosage. As that stuff just comes in the form I'm using it, there's not that much I can change about it apart from increasing or decreasing the number of milliliters per day.

Green spot algae is there, yes. Forms on the windows and rocks mostly. If I don't clean the windows, they become pretty dirty after two weeks or so.


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## Jose (12 Mar 2015)

Then your answer is to just dose more phosphates as said before. Dont make the hobby a pain for yourself.


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## jsiegmund (12 Mar 2015)

Haha, certainly not. But if I read the other comments, dosing more phosphates won't do any good as EI dosing should be sufficient. So I'd like to hear what the other guys will say about this.


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## Jose (12 Mar 2015)

jsiegmund said:


> Haha, certainly not. But if I read the other comments, dosing more phosphates won't do any good as EI dosing should be sufficient. So I'd like to hear what the other guys will say about this.



in most cases it wont.....


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## ian_m (12 Mar 2015)

ian_m said:


> Also seen people roll their own EI mixes and doses, usually missing the cheapest ingredient, MgSO4 out as they have hard water so must have Mg in it so no need to use MgSO4. Wrong.



Where is your Mg dose coming from ??? That is an essential part of EI dosing. I feel my quote above if the issue.


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## roadmaster (12 Mar 2015)

Believe Mg is in his trace .


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## ian_m (12 Mar 2015)

roadmaster said:


> Believe Mg is in his trace .


Then he is not using EI, despite stating he is.

Please dose EI.

I suspect Mg deficiency. Mg in form of MgSO4, it is the cheapest of EI ingredients, yet time and time and time and time again, people miss it out and suffer all types of plant issues. You cannot over dose Mg.



ian_m said:


> Also seen people roll their own EI mixes and doses, usually missing the cheapest ingredient, MgSO4 out as they have hard water so must have Mg in it so no need to use MgSO4. Wrong.


Taken a while to get there, but I suspect Mg issues.


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## roadmaster (12 Mar 2015)

Mg in trace for EI if using CSM+B.


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## jsiegmund (12 Mar 2015)

ian_m said:


> Then he is not using EI, despite stating he is.



What I actually stated was:


jsiegmund said:


> But still, Ferrdrakon is also perceived as a very good source of nutrients for plants. That one is dosed after lights off, 6ml / day (= 42ml / week). Recommended is 25ml / week for a tank my size. *I must admit that I haven't translated these values to EI and wouldn't exactly know how to do so*.



So EI on the macro's, "I'm not quite sure" on the micros. And since that's just off-the-shelve, I cannot change the mix. I can increase the dose or switch to using something different instead. I'm using this stuff because it was recommended to me.

But then would you agree switching to KramerDrak would solve the issue? Magnesium in Ferrdrakon vs Kramerdrak = 750 mg/l vs 3,440 mg/l. Drak specifies 10ml / week for medium lighting and 12ml / week for high lighting (on 100L). More than 15ml / week would be useless. So what if I switch out my Ferrdrakon for Kamerdrak and go with 12ml / week? Agreed that this would provide enough nutricients to remove any deficiencies there might be?

Contents of Kramerdrak:


> 20,980 mg/l potassium, 3,440 mg/l magnesium, 1,875 mg/l iron, 715 mg/l manganese, 92 mg/l copper, 80 mg/l zinc, 70 mg/l boron, 43 mg/l molybdenum, 25 mg/l cobalt, 6.6 mg/l lithium, 6.5 mg/l vanadium, 6.3 mg/l aluminium, 6.3 mg/l nickel, 6 mg/l selenium, 5.3 mg/l tin, EDTA, HEEDTA, DTPA, NTA, ascorbic acid, methyl paraben, benzoic acid


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## ian_m (12 Mar 2015)

jsiegmund said:


> So EI on the macro's,


No its not. You are not dosing EI.

A quick EI calculation of mix contents, 1 litre of EI solution up the Mg in this solution is over 7000mg/l (70gr x (molar mass of Mg)/(molar mass of MgSO4.7H2O))

Similar lower levels of K as well. This is not EI.

You have made the assumption your ferts are EI doses, they are not. You will have plant issues.


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## Rahms (12 Mar 2015)

You aren't currently dosing EI. EI is a specific amount that was found experimentally, not "recommended dosages on the back of pre-mixed fert bottles".

edit: ian beat me to it...

I don't see why you'd buy another pre-mixed fertiliser in the hope that its better, instead of just buying the powders and making your own EI micro.  You managed with the macro!


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## jsiegmund (12 Mar 2015)

ian_m said:


> No its not. You are not dosing EI.



It says "on the macro's", right? So are my doses of NO3 and PO4 incorrect? Cause then I need to find a new calculator, these are the doses the calculator gives me for my tank.

I'll won't debate over the micro's, I'm happy to say that those are not EI, never said so anyway. The NO3 and PO4 comes in weighted portions to which I only have to add 200ml of water. That's easy. Buying all sorts of powders, weighing them and making my own solution, I'm not real comfortable with that yet. That's why I liked the pre-mixed stuff, because it's again just adding water to make a stock solution. And the KramerDrak I already have, bought it some weeks ago. 



ian_m said:


> A quick EI calculation of mix contents, 1 litre of EI solution up the Mg in this solution is over 7000mg/l (70gr x (molar mass of Mg)/(molar mass of MgSO4.7H2O))



I don't understand how this is relevant. If one solution is 7000mg/l and the other one is 3500mg/l, you'd just need to add two times the amount of the second one compared to the first to get the same amount of ppm in your tank. So where you add 1ml of "EI mix", I'd add two ml of KramerDrak and the end result is exactly the same amount of Mg. One thing you could argue is that the ratios of the pre-mixed stuff might not be in line with EI, that I would need to check.


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## ian_m (12 Mar 2015)

jsiegmund said:


> So what if I switch out my Ferrdrakon for Kamerdrak and go with 12ml / week?


What 12ml a week. . No wonder. Rolling your own EI never ever ever works.

You should be dosing this weak solution at about 20ml per day if your tank is 100l.

The EI solution I gave you at 7000mg/l should be dosed 20ml per day for a 100l EI tank.

Your solution needs dosing at over 40ml per day to get the required levels. Actually get away with 20ml per day as both macro and micro.

Please dose EI, not something invented, it never works.


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## Rahms (12 Mar 2015)

Read the EI tutorial, there is no weighing.  If you can make a cup of tea you can make an EI mix.  If you're willing to go through the pain of calculating what proportion of your pre-mixed fert is equivalent to EI then go ahead it may work, but that's harder than just making an EI mix, and then you're also committed to spending more. If you're not willing to do either then, yes, you will likely have nutrient problems.

You've spent more time typing here than you would have spent on buying and making a micro mix!


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## Edvet (12 Mar 2015)

I use CSM-B from the same company (aquariumbemesting.nl i guess), i just add half a teaspoon to my (large)tank 2/3 times a week.
And i use KNO3, KH2PO4 and MgSO4 3 times a week 5/1/2 teaspoons. No algea, no problems, and it's lowish light. With high light and CO2 i used app double this amount.


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## ceg4048 (12 Mar 2015)

jsiegmund said:


> So let me ask you guys a question. If all of the tests are rubbish and you have a tank running on EI which has some sort of problem, whatever that is. How do you solve it then? Just dose EI some more and wait for it to go away on it's own? I'd say you need to have some way to at least have an indication of something to improve. And when the obvious ones (CO2, flow) are ok, then what? Or do you recon that dosing EI is sufficient to rule out any issues with nutrients / water chemistry? I'm not criticizing here, just want to understand the reasoning.


If you are dosing EI then you have ruled out nutrients as an issue. There is no point in measuring because measurements won\t tell you anything more than you can already see with your eyes, AND measuring will most likely give you false information to lead you on the wrong path. THAT'S why you shouldn't measure, because not measuring saves you from heading down the false path, and it forces you to re-evaluate things that you perhaps had falsely concluded.

Those images show a CO2 fault, especially on the p. helferi. So the problem is any combination of too much light, or not enough flow, or poor distribution of flow. Nutrients have nothing to do with those faults.

Cheers,


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## jsiegmund (12 Mar 2015)

ceg4048 said:


> Those images show a CO2 fault, especially on the p. helferi. So the problem is any combination of too much light, or not enough flow, or poor distribution of flow. Nutrients have nothing to do with those faults.



Ok, that's a clear message. So I will up CO2 a bit more to see what happens. Can you perhaps tell me how you make such a conclusion based on the images? What are the things you see that make this a clear case? I'd like to know so I can recognize the same a next time


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## roadmaster (13 Mar 2015)

I  Do not doubt that Clive can identify CO2 issues by looking at images, but for most of us ,it is a process of elimination.
If we can eliminate nutrient deficiency by following EI dosing scheme then what does that leave?


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## Rahms (13 Mar 2015)

I've always thought of melt as being a CO2 issue. Not sure if I picked that up here or even if its correct, but maybe (just maybe) its the reason


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## Mortis (29 Mar 2015)

I have a feeling that your macro mix is also quite a bit off from EI dosing. Im using the basic teaspoon measures to make my EI stock solution for 40-60Gal tanks. I mix up my ferts in 600ml coke bottles because they are easy enough to come by and using a cough syrup measuring cap to dose 30ml every alternate day. I use this because measuring caps are usually 15ml to the brim so its easy to measure without having to look at the cap and also since 30ml x 20 doses = 600ml so its all nice even numbers.

This solution contains 10 tsp KNO3, 5tsp MgSO4, 3-3.5 tsp of KH2PO4 and 2 tsp of K2SO4. In total around 20 tsp of salts and all this just barely dissolves in 600ml of HOT RO water. I have found that this seems to be pretty much the limit for EI salts that can be dissolved. My Mg is around half the recommended EI amount but I havent come across any Mg deficiencies so far and my Mg is supplemented a bit because I add some GH Booster on WC day. I have increased the phosphates a bit because with the lower amount I do get some GSA.

So your 200ml macro solution would need to have around 6.6 TSP of this mix dissolved in to make a non limiting Macro solution and you too might have noticed if it was hard to get them to dissolve in your water. Your mix doesnt have Mg or K2So4 in it so it might be easier to get into solution but even if you forget about these elements you would still need to add 30+ml of your macro mix to a 250L tank but you are adding only a few ml in each dose i think ? This leads me to believe that your Macro mix is also quite dilute and you should consider getting the individual chemicals and making your own mix.

Sorry if my post is a bit rambly but hopefully it still conveys the point I was trying to make


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