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Test Kits, Etc.

>> I continually get zero readings for nitrate and iron--seemingly
>> no matter how much I'm fertilizing.

	>It is worth testing kits with solutions known to contain the
>material of interest, just to be sure they work O.K..

Thanks for that critical piece of advice Paul.  The testing kits WERE the
problem!  The RedSea nitrate kit gave false readings of zero nitrates.  I
used a SeaChem nitrite/nitrate kit with a reference solution last night and
got consistent readings in the 2-3 mg/l range.  Confirming the reference
solution reading at 10 mg/l gave me a lot of confidence in the SeaChem kit.

The Sera Fe test kit was also in error.  I got zero readings when in fact,
the Fe level was about .16mg/l.  Again confirming the reference solution Fe
level gave me a lot of comfort.  Oddly enough, the Sera kit read about 2
mg/l (not a typo) for the reference solution of .5 mg/l but zero for the
.16 mg/l actual level in my tank.  I'm going to toss it.

>>   Phosphate readings are about .1 ppm
>> which is my guess as to why I'm growing a fair amount of algae.

The SeaChem phosphate test with reference solution consistently read about
.06 ppm (which is at least within shouting distance of the .1 ppm reading
from the RedSea kit).

>	How much is in your water supply?

There is no phosphate in my water supply.  I went with an RO/DI unit
because the water here in San Francisco has a stubborn pH of about 8.7 (I
don't know what the buffer is) and is subject to phosphate spikes (which
brought on one/maybe two algae meltdowns in my tank).  

So the phosphate must be coming from the fish and/or the fish food.  My
fish load for the 125 g is: 2 adult angels, 6 medium corys, 8 black
mollies, a dozen neons, and maybe a half a dozen Otos.  I think of this as
a light to medium load for a heavily planted tank (all of the tank is
planted with maybe 1/3rd in "lawn" plants such as Lilleaopsis and E.
tenellus).  Right?

I do maybe 3 five minute feedings over the course of an evening--Wardley
dry flakes, 3-5 Hikari algae tabs (the small ones), and 2-3 quarter inch
chunks of various frozen live foods.  Maybe this is too much?

>What is in the substrate, and are you disturbing it?  

No phosphate in the substrate, no disturbances.  (I finally smartened up
and stopped vacuuming up the Duplarit G that I plunked down my hard-earned
money for out of the substrate.)


>> I have increased the KNO3 (slowly) to a full
>> teaspoon per day (still zero nitrate readings).  I observed the
>>(roughly)2:1 ratio of K and Mg to KNO3 in the PMDD recipe--so I have been
>>increasing the K and Mg as I have tried to establish low levels of
>>nitrates in the tank.  Is this crazy?  Should I be increasing KNO3 alone?

>The K2SO4 and KNO3 should be increased together, generally.  A tablespoon
>sounds a heck of a lot, but you are quite a bit below that now.

At 1 tsp. KNO3 per day, I'm getting 2-3 mg/l of nitrate.  I thought I would
just sit tight for a week or two and see how everything stabilizes.  Per
your suggestion, I've increased the K2SO4 as the KNO3 has been increased. 
I've not increased the Mg (Epsom salts) proportionately and also noticed
Kevin's note yesterday that he's cut back on the Mg in the original PMDD
recipe.  (Would you guys consider publishing a revised recipe?)

In terms of "tweaking" the PMDD recipe, should my goal be zero or trace
phosphate levels?  If so, how is this achieved?  Will increasing the
nitrate levels (to say, 10 mg/l) reduce the phosphates further?  I was
intrigued to reread The Optimum Aquarium and see that the Dupla test
aquarium has high nitrate levels (12 mg/l, if I recall), yet is algae free.
 They reported "trace" levels of phosphate.  Maybe the German version of
PMDD starts with the high level of nitrates (10-20 mg/l) in their water
mains (as reported in TOA).

Incidentally, I was tickled to see a bit of thread algae dangling from a
couple of crypt leaves--confirming an observation I've seen in the APD that
thread algae is associated with high iron levels.  My Fe levels should have
been around .2 mg/l after the iron beating I gave my tank last weekend
(trying to get a reading out of the Sera Fe kit).  I'll drop it with a
water change to around .1 mg/l.

By the way, as soon as I pushed the KNO3 to a tsp. per day, the algae began
to recede noticibly.  In a few weeks I'm sure it will be more or less
"unobtrusive" -- beauty being in the eye of the beholder.  I'll be
interested to see if the last bits of brush algae (red) on some rocks will
be run out of town, or if I'll have to get a more efficient CO2 reactor to
deliver the final blow.

I want to thank you (and some of other APD folks who were helping off line)
for carrying me over the goal line this past week or two.  I minored in
botany (almost 20 years ago) and it is a great pleasure to be growing
beautiful aquatic plants in my living room.  Hat's off to you all, and the
APD in general.  My journey through the wilderness would have been
prolonged without you.  I'll tender the bandwidth back to some of the more
deserving folk, and enjoy the parade from the sidelines for a while.

Regards, Steve Dixon