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Re: Aquatic Plants Digest V3 #583

On Sun, 18 Oct 1998, Jeff Bodin wrote:
> So I have searched the archives and it says that holes in the leaves of 
> amazon swords is caused by a potassium deficiency. I disagree. I have been 
> pouring the potassium in my tank at the rate of 1/8 tsp KNO3/Day (in a 50g 
> water column) and the older leaves are still getting holes in them. Should 
> I increase this?
> Any suggestions?

I assume you've eliminated possible animal damage.  

If there's also some yellowing in the leaves then potassium and magnesium
deficiencies can be similar.  That's a possibility if your water is soft. 

There is a detail about nutrient deficiency symptoms that I don't remember
reading on this list.  A symptom of nutrient deficiency is caused by a
shortage of the nutrient *in the plant*.  That might not mean that there's
a shortage of the nutrient *in the aquarium*.  The plant may be unable to
get the nutrient or it might lose it too quickly to keep enough in the

For instance, Echinodorus of all types fail miserably in one of my tanks
with symptoms of both calcium and potassium deficiency.  A few other
species in the same tank also develop potassium deficiency symptoms.  This
is despite dosing the tank with enough Tetra Florapride to push the
potassium content up over 10 mg/l, adding enough potassium chloride to put
in another 10 mg/l and adding calcium carbonate directly to the substrate
around the affected plants. 

I transplanted one of the plants (an E. amazonicus or bleheri) to a
different aquarium.  I trimmed some of the damaged old growth off the
plant and the potassium deficiency symptoms never returned.  The first few
new leaves had the symptoms of calcium deficiency but after a month or so
the new leaves were normal.  Each successive new leaf now is larger than
the last.  Compared to the tank the plant came from, the tank I
transplated it into gets the same schedule of cleaning and water changes,
gets less K fertilizer and no calcium other than what comes from my soft
tap water; it's more heavily planted and has slightly less light. 

The tank where the Echinodorus fail had a coarse substrate of sealed
aquarium gravel and Tex-Blast.  The tank where the symptoms disappeared
has a more fine-grained substrate of Tex-Blast and fine river sand.  Both
substrates are very well aged and have a population of trumpet snails.  I
don't really understand why the grain size of the substrate would make a
difference, but I speculate that the roots don't function very well in a
coarse substrate and that's enough to trigger the shortage. 

Yesterday I replaced about 1/3 of the coarse substrate in first tank with
lightly washed fine sand from the nearby river.  We'll see what happens. 

I considered the idea that plant uptake of calcium and potassium is
blocked by the high sodium content in my water and that is enough to
trigger deficiency symptoms in high-light settings.  I was also able to
temporarily cure calcium and potassium deficiency symptoms by pushing
kitty litter mixed with gravel into the substrate around a plant.  The
kitty litter didn't stay where I put it, so the effect only lasted about 3
months.  I might have gotten a better result with clay balls. 

Adding nutrients to the water doesn't necessarily cure the problem and it
promotes algae growth and increases the salinity of the water.  Maybe when
plants show deficiency symptoms we should look for other possible causes
before we add more of the nutrient to the water. 

Roger Miller