Why K2SO4 and MGSO4

jrneuzil

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I am trying to follow EI as stated here by Mr Barr:
"So the aquarist dose only 3 things really, KNO3, KH2PO4 on the day of the water change then every other day there after, traces of the off day till the next week rolls around."

I see some folks are also dosing K2SO4 and MGS04. Why is that and how do you know if you need it. And if you need it, how much for a 20gal with high light and CO2 and heavy plant load ?
I searched old threads but could not find an answer that I understood. :rolleyes:

Thanks
JR
 

Roman

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Re: Why K2SO4 and MGSO4

If you have enough NO3 in tap water then instead of KNO3 you add K2SO4 for potassium.

If your water is very soft, then you need some Ca and Mg as well.
 

Greg Watson

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Re: Why K2SO4 and MGSO4

jrneuzil said:
I see some folks are also dosing K2SO4 and MGS04. Why is that and how do you know if you need it.

I think that there are a lot of "old guard" people like myself that first started out dosing twice as much Potassium Sulfate as we did Potassium Nitrate, because that was a "rule of thumb" that we used about a decade ago ...

Old habits die hard for many of us ... so there are a lot of people (including myself), that still do things because:
  1. we have always done it that way,
  2. because its cheap (and an excess of Potassium doesn't hurt anything)

.... so we keep dosing it even though we may *know* its not necessary - ...

If you are dosing Potassium Nitrate and Mono Potassium Phosphate, you are probably getting all of the Potassium that you need from those two sources ...

Greg
 

Tom Barr

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Re: Why K2SO4 and MGSO4

EI assumes the Tap water has it in there and most often it does, but it also assumes you tested it and know, so add if you need it after the water change etc.

It does not ignore it.

Regards,
Tom Barr
 

Laith

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Re: Why K2SO4 and MGSO4

I assumed that the plants were getting enough K from the KNO3. I was dosing 2.8 g 3x a week in a 200l tank, giving me about 10mg/l of NO3 (at a net water volume of 175l) 3x a week. This means I was adding about 6.2mg/l of K 3x a week.

I keep getting leaves with holes in them. Hygro gets lots of tiny pinholes and then basically older leaves "rot" at the base of the leaf and fall off. Anubia nana grows nice new leaves and then suddenly a part of the leave looks like it's dissolving and a hole forms.

All this started after a month's absence and no ferts added to the tank but that was in January.

Last week I decided to add K2SO4. I'm adding 6g at water change (15mg/l) and 2g 2x a week (just over 5mg/l per dose). This is on top of the K being added with the NO3.

I have noticed that the pearling has increased by an amazing amount. Still waiting to see if it improves my plant issues; I guess it may take a couple of weeks to impact.
 

PaulB

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Jan 24, 2005
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Re: Why K2SO4 and MGSO4

Re dosing K2S04 the potassium sulplate i obtained from a local fertilizer supply dose not dissolve well in water and leaves the water cloudy white. Is there a trick to dissolving it into water? (I am only using small amounts of it
 

Laith

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Re: Why K2SO4 and MGSO4

There must be other things in that besides K2SO4. Mine dissolves quickly and completely and leaves no cloudiness...
 

Tom Barr

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Re: Why K2SO4 and MGSO4

K2SO4 is fair insoluble compared to other ferts.

Finely ground K2SO4 will dissolve much faster though......

Regards,
Tom Barr
 

Ian H

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Re: Why K2SO4 and MGSO4

Tom Barr said:
K2SO4 is fair insoluble compared to other ferts.

Finely ground K2SO4 will dissolve much faster though......

Regards,
Tom Barr
Oh no! Not another piece of equipment I need, a pestle and mortar.

If the police ever pay a visit to my house I am well stitched up. They will do me for being a bomb maker or a mad alchemist or just a plain nutter. I would have to plead guilty to the last one. :D

Ian
 

PaulB

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Re: Why K2SO4 and MGSO4

the sulphate of potash (potassium sulphate - K2S04) is fine grade (almost like talc). are there any tricks to dissolving it into the water? i am using 1/8 teaspoon to 1 liter of water them adding it to the tank. (have tried hot water and it dosn't make much difference) :confused: :confused:
 

Laith

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Re: Why K2SO4 and MGSO4

Strange... mine is finely ground (got it from Greg) and I don't have a problem dissolving it. The solubility of K2SO4 is supposed to be 12g per 100ml which is about 2tsp per 100ml or 20tsp in a litre.

I would think that 1/8 tsp in a litre would dissolve with no problem. There *must* be something else in your K2SO4, maybe some type of binding agent or something...
 

banderbe

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Dec 5, 2005
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Re: Why K2SO4 and MGSO4

Laith said:
I assumed that the plants were getting enough K from the KNO3. I was dosing 2.8 g 3x a week in a 200l tank, giving me about 10mg/l of NO3 (at a net water volume of 175l) 3x a week. This means I was adding about 6.2mg/l of K 3x a week.

I keep getting leaves with holes in them. Hygro gets lots of tiny pinholes and then basically older leaves "rot" at the base of the leaf and fall off. Anubia nana grows nice new leaves and then suddenly a part of the leave looks like it's dissolving and a hole forms.

All this started after a month's absence and no ferts added to the tank but that was in January.

Last week I decided to add K2SO4. I'm adding 6g at water change (15mg/l) and 2g 2x a week (just over 5mg/l per dose). This is on top of the K being added with the NO3.

I have noticed that the pearling has increased by an amazing amount. Still waiting to see if it improves my plant issues; I guess it may take a couple of weeks to impact.


I doubled the amount of K2SO4 that I dose and I too noticed a marked increase in the pearling of my plants.
 

Tom Barr

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Re: Why K2SO4 and MGSO4

I toss it into the tank, in about 10-60 minutres, it's gone.
Regards,
Tom Barr