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TMG and Potassium

Chuck Gadd wrote:  "I'm going to start using TMG, and I'm planning on dosing
KNO3 separately as needed to maintain a Nitrate level of 5-10ppm. Should I
also add K2SO4 for additional potassium, or does the TMG contain enough?"
Chuck, this answer isn't definitive as I'm still doing some checking and
testing, but here in northern California under soft water, high light,
CO2-supplemented conditions we're finding that KNO3 supplements alone will
supply sufficient potassium.  I have consistently found K levels in the 20 -
30 ppm range based on KNO3 supplementation sufficient to maintain minimum
nitrate levels.  These levels seem to produce excellent plant growth and
have not been problematic for fish or resulted in excess algae growth.  I
should mention that TMG has fairly low levels of potassium (check out the
contents on the label) and doesn't play much of a role in providing
potassium in the planted aquarium in my view.

As I have mentioned before, the new potassium kit from Lamotte for $35 is a
handy investment to nail down information on potassium.  I've tested the kit
with reference solutions from Hach and it does an adequate job (that's where
I get my reference solutions, George!)

I'll let you all in on a little bit of heresy I've been experimenting with
recently.  Many of us strive to maintain phosphate-limited conditions in our
planted aquaria.  This is one of our basic algae control strategies.  But
what do we really mean by that phrase?  Can there be such a thing as having
too little phosphate?  And what does fish feeding have to do with this
issue?  Will a heavy feeding schedule provide sufficient phosphate for
"optimum" (uh-oh, I'm in trouble now :-)) growth.  My preliminary
observations are that one can have insufficient phosphate levels and that
this condition can occur in tanks where the fish are fed heavily!!!  I'm
using 1/10 gram amounts of potassium monobasic phosphate with quite
surprising results (beautiful, is actually the right word for it) under a
variety of high growth conditions.  I have a fairly good feel for what this
supplement is doing to nitrate levels (driving them down, as one would
expect).  I'm just starting to focus on the effect on potassium levels.  

More later.

Regards, Steve Dixon in San Francisco where it's rain, rain, rain and more