Adding Potassium Sorbate to EI mixes . . .

[Zeus.]

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

 

[Andrew Butler]

Hi @ian_m

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?

 

[Zeus.]

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 😉

 

[Andrew Butler]

Thanks Karl

but @dw1305 will have a more conclusive answer about that

hopefully a more simplified answer too!

 

[Zeus.]

Well the simple answer to

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 😉

 

[Andrew Butler]

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

 

[Parablennius]

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!!!

 

[Sammy I]

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....

 

[dw1305]

Hi all,

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.

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

 

[Andrew Butler]

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.

 

[dw1305]

Hi all,

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">.

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 @Guest's threads or <"@akwascape's"> <"low tech tanks">.

cheers Darrel
.

 

[Wookii]

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 😉

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.

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. 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

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?

 

[Zeus.]

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

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

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

 

[Wookii]

Watch the plants for deficiency's and act on symptoms

View attachment 131149

So trail and error and time IMO/IME



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



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

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.

 

[Zeus.]

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.

 

[dw1305]

Hi all,

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

That one.

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

 

[Wookii]

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?

 

[dw1305]

Hi all,

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