Ferts questions

[alan'67]

Firstly,sorry if these questions sound a bit dim but I'm struggling to get my head around what certain ferts do and how they react inside an aquarium.
I've read about making up a macro solution using 4tsp of Potassium Nitrate,1 tsp of Potassium Phosphate and 6 tsp of Magnesium Sulphate from ukaps sponsor aquarium plant food,(great service by the way).
My first question is that I know ( I think) that Nitrogen is plants no1 macro nutrient followed by Potassium at no2, so why is the largest amount of the macro mix with 6 tsp....err.... Magnesium Sulphate?.
Secondly, if Nitrate is the final product of the nitrifying process of the filter and only water changing removes it, why do have to add more?. Is only Nitrate mixed with Potassium useful to plants?.
Lastly,(thank god, your probably thinking), when making up an all in one solution it is recomended to keep the ph of the solution low using Ascorbic Acid to help prevent a reaction between the various salts which would then make them unavailable to the plants in the tank. What I don't understand is how that would still be the case once you pour the mix into a tank with a high ph and bright lights?, wouldn't the vital nutrients just react in the tank instead of the bottle?.
Thanks for your patience reading this drivel .

 

[PARAGUAY]

Hi Alan have you read Cegs tutorial on EI ?

 

[alan'67]

Hello Paraguay, yes mate I did have read of Cegs excellent article (several times to be honest!). In fact it was his tutorial that gave me the confidence to give EI a go in the first place.
I'll still admit to struggling to grasp just what the different powders do once in the aquarium however, hence the question why was MgS04 was dosed at such a high level compared to Kno3.
I think the reason may be Magnesium Sulphate is not a particular efficient way of introducing Mg into the tank so you just have to add extra?. I'm trying to gain more knowledge so I can convince the other half to stop buying expensive brand ferts for her tank and give EI a go.

Its not going to well to tell you the truth!.

 

[PARAGUAY]

I cant add much on this except the basic formula is as you know Tom Barrs trials and experimentation giving us this guide of the amounts of salts recommended and its the estimate to ensure the "luxury uptake" throw in the mix Toms mention different plants uptake needs Plants with high tech EI give off lots of waste when growing so the need for large water changes depleting nitrate levels.fish waste is never enough except maybe in slow growing low tech soil tanks and then theres the big tank few and small fish therefore the filtration has less but capable bio filtration needed less nitrates?So I just mix and through it in.There will be threads here discussing your specific query why not try John Whelan or TNC with the question

 

[dw1305]

Hi all,

I think the reason may be Magnesium Sulphate is not a particular efficient way of introducing Mg into the tank so you just have to add extra?.

No, all the EI salts are fully soluble.

It is because only the "Epsom Salts" (MgSO4.7H2O) form of magnesium sulphate is stable at atmospheric moisture levels, all other formulas are hygroscopic and pick up "water of crystallization". Because the stable hydrate is the "heptahydrate" (.7H2O) "Epsom Salts" only contain ~10% magnesium (Mg).

You can only get anhydrous MgSO4 by heating the salt (to drive off the water of crystallization) and immediately storing it in a desiccator, so even though it may say MgSO4 on the label it is always MgSO4.7H2O when you use it.

Secondly, if Nitrate is the final product of the nitrifying process of the filter and only water changing removes it, why do have to add more?. Is only Nitrate mixed with Potassium useful to plants?.

Plants need all the essential nutrients for growth, but in differing amounts.

I'll ignore carbon (C) and after that they need about x10 more nitrogen (N) and potassium (K) than they do phosphorus (P) and about 3x more phosphorus than any of the other nutrients. The macro nutrient are often short-handed to N-P-K.

Any nutrient can be limiting (this is Liebig's law of the minimum), but the most likely ones are N, K, P, Mg and iron (Fe) probably in that order.

it is recomended to keep the ph of the solution low using Ascorbic Acid to help prevent a reaction between the various salts which would then make them unavailable to the plants in the tank. What I don't understand is how that would still be the case once you pour the mix into a tank with a high ph and bright lights?, wouldn't the vital nutrients just react in the tank instead of the bottle?.

Yes, the answer to that one is, that they do to some degree.

If we keep the solution acidic then most nutrients remain in solution as ions. The real problem is keeping iron ions in solution in use, because nearly all iron compounds (oxides, hydroxides, phosphates etc) are insoluble.

To get around this we use chelated iron (FeEDTA etc) where iron ions Fe++(+) are released as the EDTA is photo-degraded. Hopefully the plants will get enough iron to fulfil their needs before iron phosphates and hydroxides form. It is the iron phosphate issue that means that you should add macros and micros on different days.

cheers Darrel

 

[alan'67]

Thanks Paraguay & Darrel for your replies,it's much appreciated.
Sorry to sound a bit of a thicko but I'm still not to clear why MgS04 is the largest amount of powders in the aquarium plant food mix.Reading Darrel's reply,i'm thinking it's because the MgS04 that's used is low in Magnesium content and is mostly made up of a moisture absorbing mineral,is that correct?.
Another point I would like to try to get a handle on is how effective EDTA chelators are in a tank with water above its 6.5 ph limited range.I live in Essex and use tap water with a ph of around 8 ph.Even allowing for a ph drop of approximately 1 using co2 injection, that would surely mean the effectiveness of any fertilizer using EDTA as a chelator will be greatly reduced.?
So in other words,wouldn't it be more effective to either, A: have tank water with a ph of 6.5 max so the ferts are more easily absorbed, or B: use a fertilizer with a higher ph tollerance? .
One last question if I may, if EDTA chelators react to light, is it a good idea to only dose your tank when the lights are on?.

Thank you for your time chaps.

 

[Manisha]

Hi Alan - I'm new to planted tanks too & also have read through Clive's article & thread myself, trying to get my head around ei dosing as I'm considering implementing it.

What 'I understood' (sorry if inaccurate) from the article and questions throughout the thread in relation to your question was that the values Clive is using are in relation to a co2 enriched, high light tank of 5/6 watt per gallon. Beyond 5/6 watt per gallon plants were unable to use the extra light for photosynthesis. So in a tank where light and co2 are unlimited the three macro 'foods' are added and the micro chelated mix 'foods' are added in quantities that provided unlimited nutrients to promote optimum conditions for plant growth.

Magnesium is a micro nutrient but at above levels in the chelated mix plants were observed to show magnesium deficiency so extra was added in the form of magnesium sulphate (MgSO4).

I 'think' this is why from reading the thread. Am eager to understand the process better but really struggle because I lack the basic knowledge in chemistry that experts such as Darrel and Clive have so am following this thread as you've raised some interesting question that I am curious also to understand

 

[dw1305]

Hi all,

Sorry to sound a bit of a thicko but I'm still not to clear why MgS04 is the largest amount of powders in the aquarium plant food mix.Reading Darrel's reply,i'm thinking it's because the MgS04 that's used is low in Magnesium content and is mostly made up of a moisture absorbing mineral,is that correct?.

Yes it is the <"water of crystallization"> that reduces the magnesium content. Have a look at <"Hygroscopicity and weight....">.

The calculation for "Epsom Salts" is here:

When you work out the percentage magnesium (Mg) you need to know the relative molecular mass (RMM) of the salt, by adding together the relative atomic mass (RAM) of the elements.

RAM
Mg = 24
S = 32
O = 16
H = 1

MgSO4 (anhydrous) = 24+32+(4*16) RMM = 120 and the %Mg = 24/120, so it contains ~ 20% Mg.

Add in the "water of crystallization" and you add 14 hydrogen (H) atoms and 7 (O) oxygen atoms :
24+32+(4*16) + (14*1)+(7*16) ~ 24+32+64 = 120 + 14+112= 126 ~ 120 + 126 = 246 (this is the RMM "Relative Molecular Mass" of MgSO4.7H2O)

So "Epsom Salts" have 24/246 ~ 10% Mg.

I live in Essex and use tap water with a ph of around 8 ph.Even allowing for a ph drop of approximately 1 using co2 injection, that would surely mean the effectiveness of any fertilizer using EDTA as a chelator will be greatly reduced.?
So in other words,wouldn't it be more effective to either, A: have tank water with a ph of 6.5 max so the ferts are more easily absorbed, or B: use a fertilizer with a higher ph tollerance? .

You can try FeDTPA, the details are in <"pps pro and high nitrates......">

cheers Darrel

 

[Daveslaney]

Im no expert by any mean,Stuggling to understand the basics of the chemistry to be honest
But isnt the basic idea behind EI so there will always be excess of all nutrents in the water coloum so there is no restriction to plant growth from that area making it a simple method to follow.
So even people like me have a better chance of growing plants sucsesfully.
so the short answer is there will always be excess in the water coloum?
Is there iron in the micro mix in EI?or do i need todose this to?
Regards Dave.

 

[dw1305]

Hi all,

But isnt the basic idea behind EI so there will always be excess of all nutrents in the water coloum so there is no restriction to plant growth from that area making it a simple method to follow.

I'm not an EI user, but I think you're right the idea is that for any given light (and CO2 level) nutrient availability doesn't limit plant growth.

Is there iron in the micro mix in EI?or do i need todose this to?

Depends which trace mix you use. My suspicion would be that a lot of people add extra chelated iron.

Have a look at <"James' Planted Tank: Dosing Methods">, it has a <"Comparison of traces">.

cheers Darrel

 

[Daveslaney]

Thanks Darrel.

 

[alan'67]

Hi Manisha, Cegs article certainly makes a compelling case for trying EI dosing dosn't it!.I definitely noticed a big improvement in plant health since I started using it,although my algae issues are still there. I guess you don't have to concern yourself about what salt does what if you choose not to but I find it makes the hobby more engageing when you try to understand how the different powders work.I would certainly recomend you give it a try.

And many thanks Darrel for your patience and explanations, and posting links for the detailed info, it's very much appreciated
Depending on cost and availability, I will try using a different iron chelator just for curiosity.

 

[Daveslaney]

Hi Alan
Hope you dont missunderstand my post. I wasnt say not to find out about the different salts etc. I to find it fasinating and would like to get a grip on what does what etc. Just saying i was struggling to understand it to be honest. And from what i can gather there will always be a excess of all nutrients using EI because that the way it ment to work.
I to use EI and it defiantly works for me.
Regards Dave.

 

[Manisha]

Hi Manisha, Cegs article certainly makes a compelling case for trying EI dosing dosn't it!.I definitely noticed a big improvement in plant health since I started using it,although my algae issues are still there. I guess you don't have to concern yourself about what salt does what if you choose not to but I find it makes the hobby more engageing when you try to understand how the different powders work.I would certainly recomend you give it a try.

Understanding the purpose behind adding the salts is a lot more rewardinging than following a recipe blind (and having the benefit of being able to adjust out of interest like your doing or according to your needs) - I definitely agree with but for me the theory is only part of the problem/solution.

For my tanks there are variables I can't measure (co2/par) accurately so I can't compare them to one another or to a control or a theory so...taking into account the limitations, it's trial and error and as they say 'standing in the shoulders of giants' for some things

 

[alan'67]

Hello dave, there's no misunderstanding at all mate.Just like yourself l'm trying to grasp a better understanding of the fert requirements of plants in our tanks so hopefully in time, I will become a much better plant grower.To be honest, I can't get any worse!.
While I can fully appreciate the concept of unlimited supply of nutrients, just blindly throwing a set amount of salts into my tank doesn't make me any the wiser to be honest.Although there is nothing wrong with that approach either.
We all except that our tanks differ and that E in EI means Estimated,but to my mind,unless you can get a grip of the basics of why you might want to change your fertilizer mix,ultimately you will be no better off for doing so.
I appreciate the patience of the more experienced members of this forum because they must get a little bit tired of repeating themselves but, I will admit that I struggle to get my head around the science.But plants are expensive so I can't afford to keep killing them off!.
I firmly belive patience and persistence are key to long term success with aquariums and a swear box to help fund it when it all goes wrong!.

Now having said that, if someone could point me in the direction of why people measure their Total Disolved Solids (TDS) and their importance I would be very grateful!.