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Regaurding Evil PO4

>Date: Fri, 06 Feb 1998 10:06
>From: "Dixon, Steven" <stdixon at bechtel_com>
>Subject: Evil PO4
>>Tim wrote:  Tim Mullins - Pittsburgh
>>(who has found the heretofore evil PO4
>>quite useful in my PMDD regimine as of
>Tim, what form of the evil PO4 are you
>dosing your aquarium with?

Ah, the evil PO4. Well, ok, not completely
evil, but if dosed improperly. . . algae!!!

I use KH2PO4 (MonoPotassium Phosphate)
in a 1% solution(about 1/2 teaspoon in
1/3 litre water). A one-time 1ml dose
of this strength in my 90 gallon tank
(85 G water column) boosts PO4 by about
.02mg/ltr (Rumor has it a _total_ PO4
concentration in the aquarium of .02mg/ltr
is a reasonable bogie).

Why do this????? Maybe you shouldn't.
Turns out I was quite phosphate limited
in my Dupla style 90 gallon. My particuars:

1) I've played with PMDD for awhile now.
I've altered the standard formula a bit
to increase macro nutrients to trace
ratios. My current non-standard mix is:
  5 teaspoons KNO3
  3 teaspoons K2SO4
  1 teaspoon  MgSO4 + 7H2O
  1 teaspoon  Trace (14partsCSM + 1partH3BO3)
  1/3 litre of water
Of course, everybody best tweek their own.
I dose 4ml daily of this mix in my 90.

2) I bubble dose CO2 to average 10mg/ltr.
Lighting is 200 watts of VHO aquasun. I use
substrate heating with laterite in lower
1/3. Water changes are 1/6, twice a week.
Light fish load (3 mollies, 5 SAEs, 12 Ottos),
heavily planted. Some of my nutrient levels:
  NO3 = 5 mg/ltr
  K   = 8 mg/ltr (Yes, LaMotte makes a test!)
  PO4 << .05mg/ltr (PO4 dosing aside)
  Fe  < .05
  Ca  = 60
Pretty soft water with pH averaging 6.6
after CO2 injection.

3) Ok, so what? You see, I always measured PO4
to be way below .05mg/ltr (LaMotte limit).
Good, right? But:
- Old growth on my Pygmy Swords browned 
  away. Lots O' dead leaves.
- India Star (Zosterifolia) would spirt
  and stop. Stems would rot.
- Val would spirt when first planted, then
  slowly melt (substrate depletion of P I
  suspect but can't say conclusivly)
- Newborn Crypts were staying dwarfed.
- Java Fern had minute black spots
  (other than those from spores)
- Aponogetons would use up their stores
  and languish

Over time I had tried juggling PMDD ingredients
to find what was in short supply (Mg?, Fe?, etc.)
I also tried chemical substrate additatives like
Jobes 16-2-6, Crypto Dunger, PMDD to the roots
via hypo. Only the Jobes did much (note the NPK).

I might add I have had luck experimenting
with Steve Pushak's "organic substrates"
in other tanks, but my 90 is ala Dupla style.

4) So, last resort, PO4 addition. Why a last
resort? Like I said, the evil PO4! I knew my
90 was phosphate limited. This was my goal via
Conlin and Sears. BUT. . .,apparently it was
way too phosphate limited! Since adding PO4
things have really greened up and old growth

5) Algae? Sure. Too much PO4 and I get spot
and the green velvety algae on the glass
(later easy to remove). Other types haven't
been a problem, praise be the SAE. Still,
very easy does it with PO4. I believe Conlin
and Sears really got it right!

6) I'm still playing with PO4 dosing.
Sometimes I'll add a ml to the water column.
Sometime I'll inject it via hypo into the
substrate. I sure don't put in in every day.
The plants are my guide. One observation:
if I dose KH2PO4 to the column at night,
I swear it leads to less algae and better
higher plant growth than if I dose it in
the morning with my PMDD. Can't yet say
anything conclusive though.

7) Of course I could bag all the PO4 stuff
and just add more fish (and food).   :-)

Tim Mullins - Pittsburgh

P.S. Anyone what to buy a slightly
     depleted 2 litre size of PhosGaurd
     for $6 plus shipping?   ;-)