CO2 Questions

Hi Paul,

Thanks for responding to my posting.  I'm a great admirer of your postings
and efforts to help us non-scientists take some of the voodoo out of
aquatic plant gardening.  One of the reasons I have avoided the Dupla route
is I don't want to buy "magic" potions.  I want to at least be guessing
about what is going on.  

Responses to your points/questions:

>> I have a Sandpoint CO2 setup for my 125 gal planted tank.  Starting with
>> RO/DI water, I use a carbonate buffer (Kent PH Stable) to obtain 2-3

	>Sodium bicarbonate would be cheaper.  Calcium carbonate (powdered,
>which dissolves to form the bicarbonate) would be good, too.

	I do want to move off the Kent products.  I realized that by
following their instructions carefully and not understanding what was going
on I was adding carbonate buffer and then using acids to take the pH back
down and then adding more buffer.  We should all be in the business of
selling products which use each other up!

>>The pH dropped nicely from 7.2 to 6.8 (Pinpoint pH monitor) with some
>>daily  fluctuation of .3 or so.  With 2.5 dKH and a pH of 6.8, the CO2
>>level MUST be about 12 mg/l, unless some of the stuff I'm adding to the
>>water is resulting in bad KH readings.  Right?

	>The KH readings should be O.K., provided the seachem stuff _is_
>just a (bi)carbonate buffer.

I think it is.  I'm going to try Tropica Mastergrow (per Randall) as well
as PMDD when the micronutrient mix arrives--so the question should go away.
>>My question is:  Should I be thinking about a more efficient reactor? 

	>How well are the plants growing?  You may have enough already.
>It may also be that your current method will empty the tank too quickly
>for your liking, but CO2 is cheap, and commercial reactors are not!

My plants seem to be doing fairly well.  (I'm so new to a reasonably well
fertilized aquarium that I'm not certain.)  I'm getting an inch or more
growth per week from hygo difformis and at least that much for other stem
plants including rotala indica and macandra.  Amania gracilis is growing 2
or 3 inches per week.  Java ferns, swords, bolbitis and crypts are growing
some new leaves each week, but I also continue to grow algae (mostly green
spot, but a bit of cyanobacteria persists as well).  O2 bubbles are coming
from a number of my plants.  Crypt leaves are showing some chlorosis though
(yellowish and spotting).

I seem to be having trouble establishing a P-limited tank per your paper. 
I continually get zero readings for nitrate and iron--seemingly
no matter how much I'm fertilizing.   Phosphate readings are about .1 ppm
which is my guess as to why I'm growing a fair amount of algae.

And I may be doing something really stupid with the PMDD's macronutrients
and Mg.  I'm sure that I need to supplement K (because of the RO/DI water
and the lack of significant K in any of the supplements I'm using, except
for fish food).  So I started with the 1/4 tsp. along with about the same
for KNO3 and Epsom salts.  Since I can never get a nitrate reading (and I
still have phosphate), 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?

My source for KNO3 is Cooke's "Stump Remover and Potassium Nitrate." 
Someone seemingly knowledgeable in the garden shop assured me it's all
KNO3.  The lable says "13-0-44" and guarantees 13% "Nitrate Nitrogen" and
44% "soluable potast (K2O)."  No other ingredients are listed.  Is this the
right stuff?  Would you put as much as a tablespoon of the stuff in a 125 g
daily if that's what it took to get a 2-5 ppm nitrate reading?  

I'm not sure what I should do to get some Fe in the tank (prior to arrival
of micronutrient mix).  I put the maximum recommended dose of Kent plant
fertilizer in last night (supposedly mostly chelated iron) and still
couldn't get an Fe reading (using Sera Fe test).

Re CO2 reactor efficiency:  I went to my local San Francisco aquarium shop
yesterday and chatted the staff up about reactor efficiency.  No one seemed
to have any views.  But I did read the directions/instructions for several
CO2 reactors and ran across an interesting implication.  I got the
impression from the Aqualine Buschke material that reactor efficiency might
be, in part, a function of dKH.  The material emphasized that one would
only get the stated performance at 10 dKH or greater.  It stated that for
each 10 dKH, an additional 300l of water would be fertilized.  So I'm
wondering if my 2-3 dKH level means I'll get less CO2 than if I had say,
6-8 dKH.  Do you know anything about that?

Sorry for the long note.  (I can sort of feel that after 2 years of futzing
I'm at the treshhold of establishing a decently growing planted
aquarium--so I thought I would just go ahead and ask the rest of my

Regards, Steve Dixon