Q# on Using Green Valley Trace Mix for PMDD?

["Anthony Law" <anthony at q-test_com>]

Hi all, aquatic fish & plants newbie here.  Trying to
mix my own PMDD for med-planted 72G community tank
with 110W of PC lighting.  I added a DIY CO2 system
recently & PMDD is the next logical step I assume.

Saw a very cheap local trace mix.  Cdn$4.99
(US$3.30)for 500g!  Green Valley brand from Abbotsford
BC.  It's in tiny 2-3mm pellets form & not powder.  The
contents, especially Cu, scare me though:

B 2.4%, Cu 2.4% (too high?), Fe 14.4%, Mn 6%, Mo
0.06%, Zn 5.6%

1) Can I simply scale back this trace mix, say from 1
tblsp to 0.5 or 0.25 tblsp as per SC formula?

Off Topic.  I would hate to kill more fish by
accident.  When I rigged my DIY CO2 something went
wrong.  I had decent underwater spraybar (1" from
surface) turbulence, but with temp at 81-84F, I lost 2
mating pulchers & 2 mating Dehane taeniatus (ouch) all
within 5 days after an addition of 2 big Giant Hygros
& 25 Neon Tetras.  The 4 just started breathing
heavier but all stayed hiding in caves or under plants
at the bottom of tank, not at surface.  And they just
dropped dead one by one on days 3 to 5.

All other grown fishes, including 2 marble angels, 3
pearl gouramis, 9 rams, 1 SAE, 6 corys, 40 or so small
tetras (25 of them neons) were fine & didn't show
*any* signs of distress whatsoever.  Filtration is by
1x Eheim 2028 Pro2 (for up to 158G tank) & heater is
1x 250W Ebo.  pH between 6.5 to 7.0, very soft
Vancouver water less than 1 deg KH & GH, ammonia 0,
nitrite 0, nitrate close to 0.

2) The only conclusion I got was maybe with the recent
changes, the dissolved oxygen level got too low for
these West African dwarfs but not the others? 
Thoughts anyone?  

BTW I have since reduced tank temp down to 78-81F (the
110W PC heats up the tank by 2-3F daytime).

Thanks,

Anthony.