# Adding Potassium Sorbate to EI mixes . . .



## Wookii (17 Dec 2019)

I have been advised when mixing larger batches of pre-mixed EI salts in solution - designed to be used over an extended period of time -  to add a 'pinch' of Potassium Sorbate to the mix. As I understand it, Potassium Sorbate is a preservative, and is added to prevent the mix going bad over a longer usage duration.

I plan to mix 1.5 litre batches of micro and macro mixes, which should last around 40 weeks on our new 60 litre aquarium, using an auto-doser to dose 12ml of each, every other day.

What I wanted to check is that adding this Potassium Sorbate is not going to be detrimental to fish, inverts, or the tanks biological system?

I'm assuming not, as a) the person suggesting it surely knows what they are doing, and b) a 'pinch' in 1.5 litres is a very tiny amount relative to 12ml dosage per day and the tank volume. However these things are always worth checking!?


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## papa_c (17 Dec 2019)

Reading on this previously my understanding is that you should use 1g per litre of liquid in conjunction with acetic acid to drop the ph. I've used it for my mix but strangely my ei mix turns brown but no signs or mold is visible. 

My latest batch I have just mixed with macro salts to see if it has a negative effect.

As a tip I sterilize my container with baby sterilizing fluid prior to mixing it up.


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## MJQMJQ (18 Dec 2019)

papa_c said:


> Reading on this previously my understanding is that you should use 1g per litre of liquid in conjunction with acetic acid to drop the ph. I've used it for my mix but strangely my ei mix turns brown but no signs or mold is visible.
> 
> My latest batch I have just mixed with macro salts to see if it has a negative effect.
> 
> As a tip I sterilize my container with baby sterilizing fluid prior to mixing it up.



Oxidation?


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## papa_c (18 Dec 2019)

Really no idea why!

One thing I noticed was when mixing K2SO4 in hot water to dissolve it, this turned light brown colour immediately....never experienced this in cold water.

When I add 500ml to 70g of K2SO4 it 'fizzes' wildly.

Any chemists out there that could give an educate reason? Has this affected the potassium availability?


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## MJQMJQ (18 Dec 2019)

Oxidation or reduction will change colour of solutions.Potassium is not a transition metal.Precipitation or displacement?fizzing generally is reaction btw acid and metal or metal carbonates releasing gas.Hot water has more energy hence fueling the reaction perhaps.Any other chemicals in there?Brown seems like iron ions or precipitate.Is the water murky or has any obvious particles?


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## dw1305 (18 Dec 2019)

Hi all,





papa_c said:


> One thing I noticed was when mixing K2SO4 in hot water to dissolve it, this turned light brown colour immediately.


Interesting, I wonder if the colour is actually an iron compound. Ferric sulphate ((Fe2(SO4)3)) solution is light brown/yellow and that would be my guess, what nay have happened is iron ions present in the warm water reacting with the sulphate ions (from the dissolution of the K2SO4). Reaction rate increases with temperature for most reactions, or it may be the hot water has iron ions present and the cold water doesn't. 

Do you know how hard your water is? If it was soft then a reaction involving iron ions is a lot more likely.





papa_c said:


> Has this affected the potassium availability?


It definitely hasn't affected the potassium availability, potassium salts are nearly all soluble. 

cheers Darrel


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## jaypeecee (18 Dec 2019)

Wookii said:


> I have been advised when mixing larger batches of pre-mixed EI salts in solution - designed to be used over an extended period of time -  to add a 'pinch' of Potassium Sorbate to the mix. As I understand it, Potassium Sorbate is a preservative, and is added to prevent the mix going bad over a longer usage duration.
> 
> I plan to mix 1.5 litre batches of micro and macro mixes, which should last around 40 weeks on our new 60 litre aquarium, using an auto-doser to dose 12ml of each, every other day.
> 
> ...



Hi @Wookii

I think the source of the potassium sorbate addition may have come from a site called _James' Planted Tank_. Although this site no longer exists, it can be accessed from another site called _Internet Archive Wayback Machine_:

http://web.archive.org

It is not a secured site but you are not required to divulge any personal information. I have used it many times as have others that I know. It can sometimes be a tad slow but, when you're in, just search for _James' Planted Tank_. When you get to the site, select 'Dosing Methods' and then 'All In One Solution'. There, you should find the information that you require.

JPC


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## jaypeecee (18 Dec 2019)

Hi @Wookii 

With reference to my post above, I should add that I have never used the 'All In One Solution'.

JPC


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## Andrew Butler (18 Dec 2019)

jaypeecee said:


> Although this site no longer exists, it can be accessed from another site called _Internet Archive Wayback Machine_:


Here's both the direct links:
http://www.theplantedtank.co.uk/allinone.htm
http://theplantedtank.co.uk/EI.htm

Just remember that the following ratios apply; *assuming 500ml water*
500ml water : 0.5g  E300 Ascorbic Acid
500ml water : 0.2g  E202 Potassium Sorbate



Wookii said:


> I wanted to check is that adding this Potassium Sorbate is not going to be detrimental to fish, inverts, or the tanks biological system?


I had this question before along with others, this thread doesn't directly relate but think raises a good question to why people don't use an all in one although mix. I don't think that's what your looking to do though. The ascorbic acid is there to lower the PH for the all in one. @Zeus. I think uses Potassium sorbate in his mixes and it keeps his doser pipes clean - he might comment and let you know but just use the ratio above so for each of your 1500ml / 1.5L you want .5g Potassium sorbate.


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## Wookii (18 Dec 2019)

jaypeecee said:


> Hi @Wookii
> 
> I think the source of the potassium sorbate addition may have come from a site called _James' Planted Tank_. Although this site no longer exists, it can be accessed from another site called _Internet Archive Wayback Machine_:





Andrew Butler said:


> Here's both the direct links:
> http://www.theplantedtank.co.uk/allinone.htm
> http://theplantedtank.co.uk/EI.htm
> 
> ...



Thanks - yes, I'm not combining macro and micro in a single mix - I'll be mixing and dosing them separately - I just need to ensure they stay good (and effective) for the best part of a year once mixed. So I wouldn't need the Ascorbic Acid then? Just the Potassium Sorbate, which I've managed to pick up a lifetimes worth off Amazon for a few quid. 

Any suggestions of what 0.5 grams equates to in volume - i.e. using measuring spoons?


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## jaypeecee (18 Dec 2019)

Wookii said:


> Any suggestions of what 0.5 grams equates to in volume - i.e. using measuring spoons?



Hi @Wookii 

The density of potassium sorbate is 1.363 g/cm3. So, you may be able to calculate it from that. But, why bother when you can buy a jewellery scale from Amazon for less than 20 quid? That's what I use for preparing a whole range of chemical mixtures for my fishkeeping. Measuring spoons! They're for baking, aren't they?

JPC


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## Andrew Butler (18 Dec 2019)

Wookii said:


> So I wouldn't need the Ascorbic Acid then?


It's cheap enough and won't do any harm so why not add it; works as an anti oxidant too.
Someone with a scientific brain might give you a better answer but if it's not going to do any harm and possibly do some good then I'd use it and have before, the link below is for the all in one but explains things a little
http://www.theplantedtank.co.uk/allinone.htm
I asked almost this exact question a while back so have a read of this one.  

Just have a google although I'm sure answers will vary slightly about the conversion


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## Wookii (18 Dec 2019)

jaypeecee said:


> Hi @Wookii
> 
> The density of potassium sorbate is 1.363 g/cm3. So, you may be able to calculate it from that. But, why bother when you can buy a jewellery scale from Amazon for less than 20 quid? That's what I use for preparing a whole range of chemical mixtures for my fishkeeping. Measuring spoons! They're for baking, aren't they?
> 
> JPC



Hey, I like to bake too! lol (joking) . . .More seriously though, the EI salt mixing directions from APFUK all use measuring spoon directions (in teaspoons!). As much as £20 is a good price, I'll pass for measuring 0.5g once a year lol

So at 1.363 g/cm3, 0.5g is 0.37 cm3 which is a little over 1 pinch with is 0.31 cm3 (seriously I have spoons to measure a pinch, a dash and a smidgen  )

What are the possible consequences of adding too much Potassium Sorbate - say you doubled up in error (1.0g per 1.5 litres rather than 0.5g)?


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## Wookii (18 Dec 2019)

Andrew Butler said:


> It's cheap enough and won't do any harm so why not add it; works as an anti oxidant too.
> Someone with a scientific brain might give you a better answer but if it's not going to do any harm and possibly do some good then I'd use it and have before, the link below is for the all in one but explains things a little
> http://www.theplantedtank.co.uk/allinone.htm
> I asked almost this exact question a while back so have a read of this one.
> ...



OK, fair enough - it looks like I can get a lifetime supply of Ascorbic Acid for less that a tenner also, so I'll add that to the mix! 1.5 g to my 1.5 Litre mix?


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## Andrew Butler (18 Dec 2019)

If you look at this link and read through it will tell you what they've used in the mix; which everything I've written is based on.


Andrew Butler said:


> use the ratio above so for each of your 1500ml / 1.5L you want .5g Potassium sorbate.


**important note* - this was a mistype and I had meant to write 0.6g Potassium sorbate in 1.5L water
0.2g Potassium sorbate in 500ml water (x3 for 1.5L = 0.6g Potassium sorbate)
The same would be applicable for the Ascorbic Acid if you go by the link
0.5g Ascorbic Acid in 500ml water (x3 for 1.5L = 1.5g Ascorbic Acid)

Just have a double check I've written thing correct and they agree with the link below
http://www.theplantedtank.co.uk/allinone.htm


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## papa_c (19 Dec 2019)

dw1305 said:


> Do you know how hard your water is? I



Hey Daryl,

Water is rock hard cambridgeshire water. Last time I checked out of the tap kH was around 18 based on a hobby test kit.

I have a plumbed in RO unit in the kitchen and use this for mixing my macros and micros. Good to know that it hasn't impacted the chemistry.



MJQMJQ said:


> Any other chemicals in there?



When mixing up my macros I mix kno3, mgso4, and kh2po4 at the same time in one container. Dissolve k2so4 in it's own container and them mix these together. I do it this way as I had some strange reaction when dissolving them all at the same time. I ended up with a lot of flocculation.


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## Wookii (30 Jan 2020)

Another quick question - I've been using my micro and macro mix now since Christmas, but I noticed the other day that my macro mix, which started off completely clear, now has a slightly brown discolouration as mentioned by papa_c above. Not as brown as the micro mix, but certainly well from being clear. I see nothing else in the container to suggest mould or other issues.

Is this something to be concerned about, and might it reduce the effectiveness of the mixture? It's worth noting that a separate mix I did in the standard UKAPF container, is still clear after two months - the only difference between them is the addition of the Ascorbic Acid in the now-discoloured mix.


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## papa_c (30 Jan 2020)

Hey Wookii,

I never managed to understand the brown reaction. I now don't add either potassium Sorbate or ascorbic acid to my macro and micro.

Between making each micro and macro mix I simply sterlise the containers with cheapo baby fluid. Haven't had any issues with mold growth based on a making up a months mix at a time.


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## ian_m (31 Jan 2020)

papa_c said:


> I now don't add either potassium Sorbate or ascorbic acid to my macro and micro.


You ought to really add at least ascorbic acid as that keeps the pH low (as well as helping the anti-fungicide of potassium sorbate work correctly) and keeps the chelates chelated. See graph below of how chelation  changes with pH.





Most micros, commonly used as aquatic ferts are EDTA (Ethylene-Diamene-Tetra-Acid) and will unchelate and be bio unavailable to plants, if the pH rises much above 7 ie neutral. Hard water, depending on hardness, has a pH of above 7, maybe even 8.5, in which case if used, the chelate will all come out of solution and be unavailable for plant use.


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## papa_c (31 Jan 2020)

ian_m said:


> You ought to really add at least ascorbic acid as that keeps the pH low (as well as helping the anti-



Thanks Ian

I use DPTA FE in the micro mix, Is this still required if I use RO water for dilution?


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## Zeus. (1 Feb 2020)

I do use RO water for my ferts as I get it from work. I can buy it from LFS for £0.06 per litre.
You can just mix it with tap water esp if your supply is soft, but boiling it first and letting it cool to remove temporary hardness will allow the ferts to dissolve better and less chance of the water becoming saturated when you add your salts.
However using RO/distilled water keeps the pH low of the fert solutions which help keep the salts in solution and reduce chances of mould also
I normally add
Potassium Sorbate 0.4g/L
Ascorbic Acid 1.0g/L
to my macro and micro mixes


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## Andrew Butler (1 Feb 2020)

Hi @ian_m 


ian_m said:


> Most micros, commonly used as aquatic ferts are EDTA (Ethylene-Diamene-Tetra-Acid) and will unchelate and be bio unavailable to plants, if the pH rises much above 7 ie neutral. Hard water, depending on hardness, has a pH of above 7, maybe even 8.5, in which case if used, the chelate will all come out of solution and be unavailable for plant use.


So what happens if you add it to an aquarium with a high PH; does it then become unavailable?


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## Zeus. (1 Feb 2020)

Andrew Butler said:


> Hi @ian_m
> 
> So what happens if you add it to an aquarium with a high PH; does it then become unavailable?



The dissolved salt which is susceptible to higher pHs will precipitate into a solid and be unavailible to be taken up by the plants via the Water Column (WC)

Its all to do with the equilibrium constant of the compound/salt and what effects the amount it dissolves into an ionic solution in water, in this case increasing the pH 'pushes' the equation over to the solid sate for the compound/salt and a low pH pushes the equation over to the compound/salt over to its ionic dissolved state in water.

If the solid precipitate is by the roots then the plant may be able to uptake the nutrients by other means eg 'active transport' but @dw1305 will have a more conclusive answer about that


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## Andrew Butler (1 Feb 2020)

Thanks Karl


Zeus. said:


> but @dw1305 will have a more conclusive answer about that


hopefully a more simplified answer too!


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## Zeus. (1 Feb 2020)

Well the simple answer to



Andrew Butler said:


> So what happens if you add it to an aquarium with a high PH; does it then become unavailable?



Yes in the water column if the pH is high enough for the compound/salt with it being compound/salt dependant


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## Andrew Butler (1 Feb 2020)

Zeus. said:


> es in the water column if the pH is high enough for the compound/salt with it being compound/salt dependant


Hmm so how do you fertilise an aquarium with a high PH - unsure mine is or not but curious


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## Parablennius (1 Feb 2020)

This may or may not help but I dose micros after the gas has dropped pH to below 7. I have water of 1.5d KH. I don't know whether it helps or not, I just follow my nose plus what I've read!!!


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## Sammy Islam (1 Feb 2020)

Andrew Butler said:


> Hmm so how do you fertilise an aquarium with a high PH - unsure mine is or not but curious



I think depends if you use dry salts/EI or an already made solution like tropica. With tropica they use strong chelators like DTPA and EDDHA so they work in water with higher ph, i think DTPA breaks down around 7.5 and EDDHA is about 11. But with EI dosing iron is bound by EDTA (generally) which breaks down around ph7. we can get around this if we have higher ph by injecting co2, which lowers the ph because it is acidic. If you get the ph to drop below 7 lets say from ph7.9 to 6.9, it would allow the chelators to work and not break down, i think that's how it works....


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## dw1305 (1 Feb 2020)

Hi all,





Andrew Butler said:


> Hmm so how do you fertilise an aquarium with a high PH - unsure mine is or not but curious


Because of where you live, you will have hard (base rich) water (about 17dKH/dGH) and it is unlikely your water will ever dip under pH 7, even during CO2 injection. 

Hard water is only really an issue with phosphate (PO4---) and iron (Fe+++) availability. <"Specifically in hard water in the UK"> there may also be problems with low levels of magnesium (Mg) and a very high Ca++ : Mg++ ratio. 

If you look at the <"solubility rules chart"> all nitrate (NO3-) and potassium (K+) compounds are soluble, but there are a lot of hydroxide (OH-), carbonate (CO3--), phosphate (PO4---) and calcium (Ca++) compounds that are insoluble. The OH- ions etc. <"are "bases">, and much more common in hard water. 





Sammy Islam said:


> already made solution like tropica. With tropica they use strong chelators like DTPA and EDDHA so they work in water with higher ph


You can use chelators to stop ions going out of solution, but the interactions aren't anything <"like as straight forward"> as the disassociation of KNO3 etc.

Usually we only chelate iron (Fe), because of the particular problems of keeping Fe+++ ions in solution. There are <"chelators which are more effective at higher pH values">.

cheers Darrel


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## Andrew Butler (2 Feb 2020)

Hi Darrel @dw1305 

is there a simple enough solution to making your own chelated mix more suited for water with a higer PH?

Maybe a recipe for the Macros/Micros in a hard water area and even simply turning that into an all in one?

I assume using EDDHA Fe is the best answer, however am I correct to think it's no good jut adding that to a pre existing chelated mix as the iron in that will still interact with the Potassium phosphate.

Does using a different 'type' of micro element make a difference to quatity? - I know some are different percentages so may sound an obvious question.
Good sources of the ingredients would also be a bonus.


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## dw1305 (2 Feb 2020)

Hi all, 





Andrew Butler said:


> s there a simple enough solution to making your own chelated mix more suited for water with a higer PH?


Have a look at @Zeus.'s <"FeEDDHA thread">.





Andrew Butler said:


> Maybe a recipe for the Macros/Micros in a hard water area and even simply turning that into an all in one?


You can create an "all-in-one solution" if you have low enough pH, personally I'd rather keep the iron and phosphate solutions separate. When I used <"do more of this sort of thing"> I had separate macro, trace and iron solutions.

A lot of people have great planted tanks with <"hard water">, have a look at @Tim Harrison's threads or <"@akwascape's"> <"low tech tanks">.

cheers Darrel
.


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## Wookii (2 Feb 2020)

Zeus. said:


> Well the simple answer to
> 
> 
> 
> Yes in the water column if the pH is high enough for the compound/salt with it being compound/salt dependant





dw1305 said:


> Hi all,Because of where you live, you will have hard (base rich) water (about 17dKH/dGH) and it is unlikely your water will ever dip under pH 7, even during CO2 injection.
> 
> Hard water is only really an issue with phosphate (PO4---) and iron (Fe+++) availability. <"Specifically in hard water in the UK"> there may also be problems with low levels of magnesium (Mg) and a very high Ca++ : Mg++ ratio.
> 
> ...



My tap water is around 7dKh and 12dGh, but in the tank that drops to around 5dKh - presumably due to some buffering from the soil etc.

Out of the tap, the water is around pH 7-7.2 and in the tank varies between pH 7.1 and pH 6.2 with CO2 injection.

Am I okay with the standard EDTA chelated Fe in the APFUK mix or should I add DTPA chelated Fe to my micro mix (I have a bottle of the TNC Iron (AT) mix which is DTPA chelated)?

Will an Fe test kit tell me if there is plant available iron in the water at the end of a macro dosing day (I.e. 48 hours after the previous micro dose) or will that just measure the plant-unavailable precipitated iron also?


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## Zeus. (2 Feb 2020)

Andrew Butler said:


> Hmm so how do you fertilise an aquarium with a high PH - unsure mine is or not but curious



Watch the plants for deficiency's and act on symptoms






So trail and error and time IMO/IME



Wookii said:


> Out of the tap, the water is around pH 7-7.2



Best to take pH of tap water after it has stood 24hrs as it contains lots of dissolved gases which alter the pH, if your tank is 6.2pH with CO2 then it should be fine with Fe EDTA just watch the plants. Fe DPTA is light sensitive so it breaks down in light and it is best dosed when pH is low so light is on 



Wookii said:


> Will an Fe test kit tell me if there is plant available iron in the water at the end of a macro dosing day



It might tell you there is Fe or no Fe but do you trust the test kit ? is lab grade or hobbyist level ??? again watch the plants and treat the symptoms


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## Wookii (2 Feb 2020)

Zeus. said:


> Watch the plants for deficiency's and act on symptoms
> 
> View attachment 131149
> 
> ...



Thanks. So is EDTA not light sensitive then, or just that DPTA is more so?

On the test kit - I appreciate these are often frowned upon in this forum, but I think they are useful if used in the proper context. I wouldn’t rely on one for an accurate measure of, for example, the absolute iron level, but I would like to hope they don’t give a false positive for existence of any iron - as long as I have excess iron available all the time between doses, then that’s enough for me.

Whilst I agree that plants are, of course the best indicator of a deficiency, I’d prefer - given that I’m EI dosing - to try ensure a deficiency doesn’t occur in the first place.

My only concern then, is that a false positive can’t occur if it is possible that precipitated iron, unavailable to the plants, could cause a positive reading for the existence of iron in the water.


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## Zeus. (2 Feb 2020)

If all the salt had precipitated out then non would be in the water column and the test result would be negative - dependant on the pH OFC, as some of the Fe may still be in solution as its not an all or nothing its all about the equilibrium of solid and dissolved ionic compound for a given pH. Plus hard water with lots of other ionic compounds makes it tricker again as there are other ionic interactions I have been advised which makes hard/very hard water complex.


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## dw1305 (2 Feb 2020)

Hi all,





Zeus. said:


> if your tank is 6.2pH with CO2 then it should be fine with Fe EDTA just watch the plants.


That one.





Wookii said:


> I think they are useful if used in the proper context.


You can test for iron fairly easily via colorimetry, mainly because a lot of iron compounds are both <"coloured and insoluble">. 





> .........all the iron ions present in the samples was reduced to Fe2+ ions by ascorbic acid. In the presence of the medium thioglycolate, a purple complex was formed because of Fe2+ reacts with a trizine derivative. The complex was determined photometrically by using UV-Vis spectrophotometer........


Having said that, there is no way that even accurate testing is going to <"tell you anything that the plants can't">, and it is only a snap shot at any moment.

cheers Darrel


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## Wookii (5 Feb 2020)

Well, I'm still seeing plenty of iron in the water, via the test kit, 48 hours after the EI Micro dose - even with 25% daily water changes - so should I assume I don't have an issue with Fe availability? Is it safe to assume the cae is the same with the accompanying micro elements, if I am EI dosing with the APFUK mirco mix?

My Macro mix seems to be turning darker brown with every passing week though - it's darker brown than the micro mix now - what are people thoughts on the cause of this? Is it likely to be ruining the mix and salts within it, and should I be thinking about re-mixing a fresh batch without the Ascorbic Acid? As mentioned previously, I have a different bottle of macros that I mixed two months ago without Ascorbic Acid, and that is still clear?


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## dw1305 (5 Feb 2020)

Hi all, 





Wookii said:


> I'm still seeing plenty of iron in the water, via the test kit, 48 hours after the EI Micro dose - even with 25% daily water changes - so should I assume I don't have an issue with Fe availability?


I'd look at this from the other perspective, if the new leaves on the plants still show iron deficiency then the test isn't accurate. 

Aquarists often look at <"water testing results as empirical proof">, but scientists tend to be a bit more sceptical and actually use <"bio-assay techniques a lot">,  mainly because they are a sensitive indicator of water conditions. 

cheers Darrel


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