Re: HELP & Chelated fertilizer

 Re your problem tank. Gosh, this is an odd one.
Are you using a pH controlled CO2 system? That might
account for the odd readings if a large amount of
base were added. It seems more likely that something
in the tank went bad and released a lot of something
which affected the accuracy of your CO2 measurement.

Perhaps there is a dead fish under the gravel? Plants
don't usually give off so much toxins when they die
and that should have been obvious. I think I'd hook
up the diatom filter to remove the cloudiness and
anything else it will take like bacteria etc. Carbon
filtration is also a good plan. If you have a spare
unused tank; I'd set it up with water from the other
safe tanks and filter material from them and put all
the fish from the bad tank in there. If it starts to
get high ammonia, keep the pH low and you can use an
ammonia absorber. Hopefully that's not necessary and
you can get biological filtration happening or add a
bunch of spare hygrophilia and lights to use up any 
extra ammonia.

Once you got all the fish out of the affected tank, I'd
half drain it and use my nose to see if there's anything
bad in there. Can you account for all of your fish
that were the burrowing kind? Snails? Perhaps the fish
that died was the sick one that was the source of most
of the contaminants.

Re: chelated micro-nutrients

It sounds interesting. I wonder about the chelating agent
though; it is usual to use EDTA (ethylenediaminetetraacetate)
Perhaps someone better informed will be able to offer an
opinion on this one. What was the commercial name and
manufacturer? Perhaps someone with a small tank would be
willing to set up an experiment.

Here's some material from my chem book on the subject of

"[Complex organic compounds] consist of a central metal
cation to which several anions and or molecules (called
ligands) are bonded." 

"[ligands forming only a single bond] with the central
ion are referred to as unidentate (Latin, one toothed)."
Some ligands are capable of two bonds and are referred to
as bidentate and can form rings with the central metal
ions. These metal complexes are called chelates (Greek, claw!).

EDTA is capable of forming a very stable complex with the
calcium ion. This explains why peat is excellent for reducing
hardness since it is a source of EDTA.

EDTA looks like this:

-O2C--CH2                CH2--C02-
         \              /
         /              \
-O2C--CH2                CH2--C02-

Chlorophyll is a chelate of Mg and Heme, of hemoglobin is a
chelate of Fe! Both of these contain quadridentate ligands.

I couldn't find any information about the solubility of
Fe-EDTA or Mg-EDTA. Presumably these complexes don't
dissociate (separate into ions) in solution but that doesn't
mean they are insoluble either. There were very little or
no precipitates in Tropica Master Grow however Floreal contains
quite a bit of large flat crystals. :-( TMG uses EDTA is the

The purpose of chelating trace minerals is to prevent them
from forming oxides or carbonates where the metal ions 
become virtually unavailable.

Note that CO2 and Ammonium ions are important building blocks
in the chemical building blocks that plants use.

Hope I haven't bored everyone to death (again ;-)

 - Steve

PS. Logged in from home and using a primitive terminal emulator.
Guess next time I'll use the modem software that came with OS2
Warp. I miss my X-windows editor!