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Re:Potassium deficiency?

    * From: "Daniel Larsson" <defdac at hotmail_com>

Hello folks!

I'm currently using PMDD in all my aquariums and I dose the ingredients
Traces(TMG), KNO3, K2SO4 and MgSO4 individually to get the amounts right.
No matter how much I dose K2SO4 (4 ml K2SO4/day in 29 liters aquarium) the
Hygrophila Polysperma and Cardanine Lyrata seems to suffer from potassium
(K) deficiency. See the following pictures of a 29 litres aquarium:
Is this potassium deficiency? If so, which dosage of K2SO4 do you recommend?

Also my JBL NO3 test kit and Tetra teststicks never shows any sign of
indicating any nitrate in my bigger 310 litres tank (when I add a drop of
KNO3 to
the tests they goes through the roof though - so the tests are working
and isn't due).
When I added 12 ml KNO3/day for a week the tests started
to indicate extremely low nitrate-content but I didn't continue this dosage
as it
feels way to much. Which dosage KNO3 do you recommend?
(310 litres tank is pretty much overgrown: )

I looked at your pictures, and I don't think you have potassium deficiency.
I thought I saw a little bit of die-back on older leaves, but considering
all the potassium you say you are adding, it might be magnesium deficiency,
which looks similar to potassium deficiency, in that both deficiencies
involve die-back from the edges of the older leaves.  In potassium
deficiency, the leaves get more "holey",  In magnesium deficiency, they
tend to die back more from the edges.  They also tend to stay green along
the central vein and yellow elsewhere in magnesium deficiency.  With K
deficiency, depending on the species, the leaf can stay green as holes form
in it and it gets lacey, or it can turn yellow.  You don't usually see a
green central vein and the outer parts of the leaf yellow in K deficiency.

I would say, keep up the nitrate additions so that you always have a
measurable amount of nitrate.  Don't forget about phosphate, too.

Paul Krombholz in cool central Mississippi, where my ISP has acquired a new
name and lost the ability to even bill me for its services.  Wonder how
long it will last.