Dosing Potassium

idylldon

Junior Poster
Sep 9, 2005
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I'm a bit confused whether or not I need to add postassium.

I currently am using the EI method with the following dosing for my 55-gallon tank:

1/2 tsp. KNO3 3 days a week.
1/8 tsp. KH2PO4 3 days a week.
Traces 10ml 3 days a week.

Using the fertilator and Chuck's calculator, it seems as though I'm not getting close enough to the recommended level of 20 ppm for potassium. I just received some potassium sulfate and was wondering if I should use it to boost the potassium level up to 20 ppm.

BTW, I'm just starting week three of the EI method and have noticed a major improvement in plant health and growth. I even had to prune a few of them during today's water change.

Cheers,
--
Don
 

Spar

Guru Class Expert
Jun 5, 2005
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Dallas, TX
Re: Dosing Potassium

you are getting 18ppm already of K, which is really good enough. I wouldn't bother with K2SO4 to gain more K.

plus, do you really have 55 gallons of actual water in there? keeping in mind that substrate, dirftwood, decorations, etc, etc, all take up space. You probably have more like 45-50g's or so. which would bring you much closer to the 20ppm mark.
 

Paul

Guru Class Expert
Jan 24, 2005
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Droitwich, UK
Re: Dosing Potassium

Spar said:
you are getting 18ppm already of K, which is really good enough. I wouldn't bother with K2SO4 to gain more K.

Might be being slow here, but can you tell me how come theres 18ppm already please? :confused:
 

Spar

Guru Class Expert
Jun 5, 2005
123
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Dallas, TX
Re: Dosing Potassium

in 55g's (US Gallons) of water:

KNO3 - 1/2t = 4.8ppm x 3 days = 14.4ppm
KH2PO4 - 1/8t = 1ppm x 3 days = 3ppm

so total K of 17.4ppm added per week.
 

Greg Watson

Administrator
Staff member
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Jan 23, 2005
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Re: Dosing Potassium

idylldon said:
I'm a bit confused whether or not I need to add postassium.

I currently am using the EI method with the following dosing for my 55-gallon tank:
If you are following the EI method and have high light ... then you are definately getting all of the Potassium that you need from the Potassium Nitrate and Mono Potassium Phosphate that you are dosing ...

There are still a lot of old guard guys (like myself included) that may still dose Potassium or might even try to tell you that you need to ... but you probably do not need to dose it ...

A long time ago (not so very long ago), when lighting levels were much lower, we often got a greater percentage contribution of Nitrate from our fish food and fish waste, thus there was frequently a need for supplemental potassium - in most aquariums today, that just is not the case any longer ...

A long time ago (not so very long ago), when we were not dosing Mono Potassium Phosphate, we were also not getting that contribution of Potassium, thus there was frequently a need for supplemental potassium - in most aquariums today following the EI approach, that just is not the case any longer ...

Even today, some people are using Tropica Master Grow for their micro nutrients ... which is 79% Potassium ... Now why you would want to spend the money on TMG for 79% Potassium when you don't need that Potassium, I don't know ... but you DEFINATELY would not need supplemental Potassium in this case !!!!!!

... do you see a trend here ?????

There may be a lot of people (including myself) that are still dosing extra potassium ... but in almost all cases, it is not necessary ...

So ... do I still dose Potassium Sulfate? Yes ... its tough to teach old dogs new tricks ... and so while I follow the EI dosing recommendations, I figure Potassium Sulfate is cheap, I'm going to dose it anyway and flush any excess at the end of the week ... but I can promise you, I do not need it ...

Of course, all of this is on the assumption that you have a 1.5++wpg gallon tank ... less than that with a heavy fish load, and you can disregard everything above ...

Greg
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
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Re: Dosing Potassium

There is no negative effect from adding K2SO4 once a week after a water change(say 1/4 teaspon per 20 gal of tank).

If there is a positive gain, I have not seen it, in some cases you might want to add extra K+ if you have high fish loads etc.

Regards,
Tom Barr
 

idylldon

Junior Poster
Sep 9, 2005
5
0
1
Re: Dosing Potassium

Thanks for all the great replies! I have about 2.8 wpg and a fairly light fish load, so I'll just keep to my original dosing schedule/amounts and forego the extra potassium for now.

Cheers,
--
Don