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Re: Nutrient deficiency symptoms related to lighting?

On Sunday, September 28, Roger Miller described symptoms---lesions on older
leaves leading to loss of the leaves---that did not improve with additions
of potassium or magnesium, but did improve considerably when the lighting
intensity was reduced.  Basically, the symptoms got worse when the lighting
was increased and got better when it was decreased.

He said:

>.....So this *appears* to have been a lighting problem rather than a nutrient
>problem, but it leaves me with a bunch of questions:...........

Roger, this looks like like a fine opportunity to do some experiments, and
I hope you see it that way rather than a tank full of sick plants that need
emergency first aid, and who cares about experimenting.

You asked if the recovery was due to delayed response to the two weeks of
increased flow through the gravel.  You can find that out by starting up
the flow again and changing back to the higher light level.  If the plants
get worse again, then you can rule out increased water flow through the

Next, I would recommend you try a plant potted, not in kitty litter, but in
ordinary topsoil that you get somewhere near your home from relatively
undisturbed soil where untended plants are growing.  In most places in
North America, the topsoil has a considerable amount of iron, which gives
it a yellowish color.  The kitty litter we use (for our cats, not our
plants) is grey, and I wonder how much iron it has.  It would be
interesting to see if H. corymbosa still shows the lesions when potted in
topsoil.  If it does, and you are sure you have the potassium and magnesium
taken care of, then we may have to consider some kind of toxicity peculiar
to that aquarium.  Toxicities  can mimic nutrient deficiencies.  I once had
a toxicity problem that exactly mimicked calcium deficiency.

On the other hand, if the potted plant does any better, then it may be a
nutrient deficiency of some sort---something supplied by the topsoil.
Generally, plants can get by on a lower level of nutrients with less light.
I have seen, for example, tanks that are lit more brightly in one area
where the plants in the bright area showed iron deficiency , but not the
plants in the dimmer areas.

I think that if the plant in the topsoil did well, I would try a big dose
of iron for all the plants.  That would be chelated iron and nothing else,
just in case some of the accompanyning micronutrients in your Flora Pride
may get so high as to be toxic.  I would get the iron level up to around
0.3 to 0.5 PPM and see what the plants do.  I know that your symptoms don't
resemble iron deficiency, but I am wondering if mild iron deficiency and
bright light might combine to make the plant unable to get enough potassium
or magnesium.  I can send you some FeDTPA, if you need some.

Paul Krombholz in Jackson, Mississippi with pleasant fall weather.