# potassium deficiency



## Ezekial (May 16, 2008)

I've been trying to do a low light, no CO2 fish tank with plants for some time. Recently (May), I noticed that the older leaves on my anubias were yellowing and developing holes in the middle and was steered toward a potassium deficiency. 

I've since started dosing with Flourish Potassium but i'm not sure if I'm dosing enough, etc. How will I know if it's enough? I am getting new growth.


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## Seattle_Aquarist (Mar 7, 2008)

Hi Ezekial,

Are your older leaves still turning yellow and developing holes? If not, you are probably doing the right thing! The dosage suggested on the bottle should be fairly accurate since you are not doing high light or CO2.


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## Ezekial (May 16, 2008)

It's hard to say with regard to the older plants as most of their leaves were that way. I did add 2 new anubias and they have developed a couple holes in a couple leaves but seem fine otherwise. It's been about 3 weeks since I've had them.

I guess I just don't know how long it should be before I see something. How often should I dose? The bottle says every few days. Also where can I find K2SO4 in bulk, this Flourish stuff is expensive if I'm going to be dosing regularly.


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## Veloth (Jun 25, 2008)

I get all my ferts from HERE. Always have had good results dealing with them.


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## Ezekial (May 16, 2008)

Thanks I just ordered some from them. Is there a way to measure potassium in the tank? I think I will need this in order to know how much to dose.


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## Zapins (Jul 28, 2004)

Measuring potassium is very expensive and very inaccurate (potassium is probably one of the most difficult nutrients to accurately measure). Also, there is really no need to measure it since potassium is pretty benign, you can add dozens of ppm of it without any adverse effects.

The old anubias leaves could just be dying off due to old age. Or... it might be phosphate deficiency. Potassium deficiencies usually start as tiny pin-holes in the leaves that enlarge over time and are surrounded by yellow tissue. If the holes are larger then pinholes its probably not potassium.


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## Ezekial (May 16, 2008)

The holes are a little larger than pinholes but I tested for phosphates (I think) and had plenty, too much actually if I remember right.


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## clearleaf (Oct 4, 2008)

In a similar situation with my 10g tank, very high phosphates (about 2ppm in my tap water, plus I was dosing it with dry ferts) but showing potassium deficiency. Actually, from what I can tell, my h. polysperma (hygro) showed potassium deficiency (small holes surround with yellow) and my h. difformis (wisteria) showed calcium deficiency (leaved curled down, very white underneath), but not vice versa. 

I would throw in a 1/4 tsp of K2S04 every three days, magically the pinholes would disappear unless the snails had snacked on the damaged leaves - then those leaves were essentially marked for death but would melt off and new leaves would be healthy. And yea, from what I understand its fairly benign - excess potassium shouldn't cause algae issues or problems to fish. 1/4 tsp into 10g x3 days with weekly water changes was fine for me.


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