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PMDD: Sources and Doses Round 2
In response to questions on PMDD, here's
an update on my post on where to buy PMDD
(poor man's dosing drops) and how to use it.
Hope this helps (many thanks to those who made
comments, sorry this has gotten so dang long):
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A) Sources for a chelated trace mix:
1) Plantex's "CSM" 1-905-793-7000 $30 US for 5Lbs
314 Orenda Ave, Brampton, Ontario
L6T1G1 Canada
(Thanks to Kevin Conlin)
For breakdown, see part E
2) Miller Chemical & Fertilizer's "Microplex"
Hanover, PA
Distributor: NitroPhos 1-713-530-5558
(Thanks to Doug Skokna)
I've never tried Microplex, but it has;
Mg-5.4% Bo-0.5%
Co-0.05% Cu-1.5%
Fe-4.0% Mn-4.0%
Mb-0.1% Zn-1.5%
3) Some Hydroponics and local garden shops
have trace mixes. But, check their ingredients
list to make sure they do not have N, P or K
(i.e. just trace mix, not something like
Miracle Grow), they're chelated, and that
their trace percents are similar to CSM.
Some folks feel Cu (Copper) should not be included
in a PMDD trace mix (it can be quite toxic to plants
and fish in high concentrations). It is in Microplex
and CSM. I haven't had any problems with CSM though
I do change 25% water a week. I know many have had
success with Microplex too. If you use another trace
formulation, you might want to be sure its Cu isn't
to high.
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B) Sources for MgSO4 and H3BO3
1) MgSO4 is available from just about any drug
store as Epsom Salts. $2 buys a lot. Note it's
hydrated (the form PMDD calls for) so it's
formula is MgSO4 + 7H2O.
(Thanks to Karen Randall)
2) H3BO3 is Boric Acid, a source of Boron. Also
available from drug stores, a couple buck buys
around 250mG, a lot.
(Thanks to Paul Sears)
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C) Sources for KNO3 and K2SO4
1) ECO Enterprises 1-800-426-6937
1240 NE 175th Street, Seattle WA
98155
KNO3 $5.98/ 5 lbs Agro grade
K2SO4 $5.98/ 5 lbs Agro grade
(Thanks to Doug Skokna)
2) PCI Scientific Supply
1-800-432-4136
KNO3 $16.75/500mG Lab grade
K2SO4 $15.50/500mG Lab grade
(Thanks to Tom Polk)
3) Local Hydroponics and Garden Supply shops.
Note: Greenlight's "Stump Away" is pure KNO3 .
5) Home Grown Hydroponics
http://www.hydroponics.com/RAQ/RAQ-aquatic.htm
(Thanks to Suwat Phruksawan & Louis Lin)
I've not checked them out
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D) Source for complete pre-mixed PMDD per original
Conlin-Sears formulation:
1) Neil Schneider, Poway CA, PacNeil at worldnet_att.net
$30 for dry ingredients to make 5 liters of PMDD.
(Thanks to Neil for making it easy)
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E) How and Why to roll your own PMDD with Plantex CSM:
1) As noted by Tom Polk, Plantex's new CSM has no
B (boron) and therefore needs to have some added.
For a ratio of 7Fe to 1.26B (5.5 to 1)
- mix 14 parts CSM to 1 part H3BO3 (Boric Acid) by
weight (about 10.5 tspns of CSM to 1 tspn H3BO3).
Here's the breakdown of CSM before and after adding Boron.
Regular CSM CSM+B
Fe 7.0% 6.53%
Mn 2.0% 1.87%
Mg 1.5% 1.40%
Zn 0.4% 0.37%
Cu 0.1% 0.09%
Mo 0.05% 0.05%
B 0% 1.18%
Co 0% 0.00%
2) Sears and Conlin's latest PMDD formula: mix
with water to make a 500mg solution,
1 tspn trace mix "CSM+B"
1 tspn MgSO4+7H2O
2 tspn K2SO4
1 tspn KNO3 (more or less, depends on your nitrate)
Some mixing notes:
- Some kinds of agro grade K2SO4 give off a gummy black
goo when mixing. Just remove it best you can by wiping
it off your mixing tool.
- The CSM+B should be completely dissolved. Try crushing
any undissolved crystals with you mixing tool.
- The KNO3 may have trouble becoming completely soluble
and a fine particulate will settle on the bottom. That's ok,
just shake the PMDD before use.
- Some say to mix up PMDD with distilled water. I've found
regular tap water works ok for me.
- Why add the MgSO4 when CSM now has Mg (it didn't use
to)? CSM doesn't have enough Mg to meet PMDD ratios.
And yes, with the dry chemical quantities you no doubt have
acquired, you could make enough PMDD to fertilize Lake
Erie <g>.
3) So why bother with PMDD when you can buy products like
Flourish, Dupla Drops, Terrafit, etc?
- Well. . . try them. If you meet with success at a
reasonable price, great!
- While requiring an initial outlay, PMDD is cheap over the
long run (hence, PMDD: poor man's dosing drops).
- PMDD trys to provide a balance of fertilizers. Not to
cast aspersions, but it's more than "Iron Water".
- With PMDD, you know what you've got. As you gain
experience, you can experiment.
- It yields results comparable to some far more
expensive brews.
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F) How to store PMDD
<<< I'd be sure to keep PMDD chemicals >>>
<<< away from the kids ! Some are nasty.>>>
1) Unmixed PMDD constituents are stable enough.
The chelated trace mix should be kept dark, dry
and not unduly hot.
2) Some say mixed PMDD will degrade over time and
even develop mold. Things that help:
a) Put your PMDD in a dark brown or opaque
bottle. Light can destablize chelates.
b) I refrigerate my main stock (mark it well so someone
doesn't take a swig) and leave a small 50ml bottle
by the aquarium for convenience.
c) Since dry ingredients are more stable, only
mix up a few month's worth of PMDD at a time.
d) Some people add a little HCL to the brew; never
tried it myself.
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G) How to dose PMDD
1) I'D GO SLOW AND MEASURE RESULTS!!!
Track Fe and NO3 with test kits and watch how
plants and unwanted algae respond. It takes
awhile (weeks) to safely ramp up and stabilize
fertilizer concentrations. More PMDD is not
necessarily better and, although somewhat
fault tolerant, too much too fast can be
injurious to plants and fish.
2) As a starting point, for each ten gallons of a heavily
planted, well lit, CO2 injected tank with 25% of water
changed each week, try around 1/4 ml of PMDD
a day. So, for a 29 gallon tank, start with 3/4 ml PMDD
a day. If you don't change as much water, you might
want to dose less.
3) Many seem to recommend dosing PMDD to maintain
around 0.1mG/ltr (0.1 PPM or Parts Per Million)
concentration of Fe (Iron) in the aquarium
and letting the other element concentrations
fall where they may. Consensus is exceeding 0.2mG/ltr
Fe is counterproductive. Again, expect to take awhile
to build up to a 0.1mG/ltr Fe level.
So, what if use of laterite raises your Fe levels too?
I'm not really sure though I use laterite, limit PMDD
doses to keep overall Fe levels below 0.1mG/ltr, and
still achieve ample fertilizer concentrations.
Suspecting that to much Fe can promote algae growth,
Steve Pushak notes he only adds sufficient Fe
to keep plants growing without symptoms of chlorosis
or iron deficiency (yellow or pale leaves), a level that
may fall under .1 mG/ltr Fe. He has found Salvinia to
be a good indicator plant for Fe dosing.
Oh, SeaChem, Red Sea, Tetra, Dupla, Hach,
LaMotte all make Fe test kits. Prices and ease of use
very widely, I like the pricey LaMotte myself. Try
"That Fish Place"; 800-733-3829 or
"Pet Warehouse"; 800-443-1160.
4) The target for NO3 (nitrate) is said to be about
5mG/ltr (5 PPM). If your aquarium NO3 already
exceeds 5mG/ltr, you ought to initially reduce or
eliminate the KNO3 from the PMDD formulation.
You might notice, however, that as PMDD begins
to balance things out by providing other fertilizer
components, your levels of naturally occurring NO3
will fall to the point where you'll need the KNO3.
Though, if you do ultimately reduce or eliminate KNO3
from the mix, don't worry about having also reduced
the K. The K2SO4 seems to provide enough.
Many of the folks that make Fe test kits also make ones
for NO3. Check that they're accurate in the 5mg/ltr range.
5) I don't know what a good target for K (potassium) is.
It turns out to be really difficult to measure anyway.
Since PMDD is rich in K, and I've read you can have a fair
bit of excess K without harming aquatic life, I wouldn't
worry about it.
6) PMDD has no P (phosphate). According to work by
Sears and Conlin, having the P in N-P-K as your limiting
major fertilizer factor helps reduce algae. Of course plants
require some P (.02 mG/ltr a good target), but you'll no
doubt have more than enough supplied by fish food and
the like.
Most terrestrial plant fertilizer supplements have a lot
of P. They may also have N in the form of NH4 or NO2
(quite toxic to fish unless dosed very very carefully). That's
why the advice to not use otherwise fine products like
Miracle Grow.
7) Why daily PMDD doses rather than a weekly mega-dose?
-Some constituents of PMDD are not terribly stable (like
chelated Fe) and may loose potency in the aquarium over
the course of a week.
-You avoid concentration "spikes" that fish might not
appreciate.
-Even if PMDD fertilizer ratios aren't perfect for your
situation, you will have at least some of whatever your
limiting factor is available each day.
8) Most drug stores sell droppers marked in mL for
dispensing medicine. The 2.5 to 5mL sizes work
great for metering out PMDD. Oh, when dosing,
I'd first shake the bottle in case of settling, then
try to stir the PMDD slowly into the aquarium so
fish don't get hit with a "chemical cloud".
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H) Some of my dosing experience
Did I follow my own advice and go slow . . . no. <g>
I initially dosed with 5ml PMDD a day in my
45 gallon tank (40 gallon water column).
I changed 25% of my tank's water each week.
If you assume no Fe depletion (a poor assumption
but good for establishing an upper bound) my
Fe concentration would have eventually leveled
off at 0.4mG/ltr. Too high! So, once I reached Fe of
0.1 mG/ltr (took about 2 weeks at the 5ml dose), I
reduced my PMDD dose to a little over 1 ml a day.
My plant growth really improved. :-)
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I) PMDD constituents
PMDD s breakdown by element:
approx G/Ltr % of total Ratio to Fe
N 1.41 6.41% 3.06
K 13.80 62.53% 29.84
S 5.19 23.50% 11.21
Mg 0.95 4.32% 2.06
Fe 0.46 2.10% 1.00
Mn 0.13 0.60% 0.29
Zn 0.03 0.12% 0.06
Cu 0.01 0.03% 0.01
Mo 0.00 0.01% 0.01
B 0.08 0.38% 0.18
Co 0.00 0.00% 0.00
And two important quantities
NO3 6.26 -- 13.54
SO4 15.56 -- 33.63
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J) Nerd stuff on calculating aquarium
PMDD constituent concentrations.
1) Figuring the change in aquarium concentration of Fe
(or any element) after a single PMDD dose:
Increase in Concentration in PPM =
(PMDD concentration of element)*(Dose)/(water column)
in mG/ltr or PPM in ltr in ltr
my case: 5ml PMDD, 45 gallon tank (40 gallon
160 liter water column), and Fe is of interest.
[(0.46G/ltr)*(1000mG/G)]*[(5ml)*(ltr/1000ml)]/(160ltr) =
_0.0144 mG/ltr Fe_ increase in aquarium as a result of a dose.
Of course, to figure it out for multiple daily doses (no
water changes), multiply by the number of doses.
2) Figuring the cumulative change in aquarium concentration
of Fe (or any element) in PPM after long term daily PMDD
use with periodic water changes:
The tricky part about figuring this is knowing depletion rates.
I can figure out how water changes will deplete an element,
but I don't know how much plants will. Well, since my intent
is to avoid overdosing Fe, I'll look at the worst case: one
where no Fe is used by the plants (sure, a rotten assumption
since the whole point is to provide Fe, but it does yield an
upper bound or maximum possible concentration).
Turns out concentration buildup given periodic water changes
is one of those Geometric Series things.
Say "D" is the total concentration increase after multiple PMDD
doses preceding a water change (figured in PPM per part 1).
Say "R" is the portion of pre-change concentration
that remains after the water change (ie a 25% water change
leaves 75% of concentration). Well, after 6 weeks,
you'd have a cumulative concentration of:
(((((D*R)+D)*R+D)*R+D)*R+D)*R+D or
D*R^5+D*R^4+D*R^3+D*R^2+D*R+D or
SUM n=0 to 5 of (R^n+D)
Now, over many many weeks you'd have a cumulative
concentration of;
SUM n=0 to infinity of (R^n+D) or
D/(1+R) Simple result, huh?
So, using this secret formula D/(1+R) and putting it in
terms of daily doses, days till water change, and % water
change (note: % water change = (1+R)):
Long Term Cumulative Increase in Concentration =
(daily increase from dose)*(days till change)/(% water change)
in mG/ltr or PPM in days in decimal
only valid if water volume
change >> dose volume
Carrying over the example from part 1): 5 ml PMDD dose
daily, but with 25% weekly water changes;
(0.0144 mG/ltr Fe)*(7)/(0.25) =
_0.4mG/ltr Fe_ final aquarium concentration
Yikes, 4 times too high! That's why I ended up leveling
off at a lower PMDD dose, about 1 ml a day, for my 45
gallon tank.
Again, this all assumes no depletion, a lousy assumption,
so I'd measure Fe as you go. As I said, this calculation is
only good for an "upper bound".
K) So, just add PMDD to your water column and your plants
will grow like weeds? Well . . . maybe. There are other
factors to investigate. Some feel substrate fertilization is key
to success with some plant species. Others swear by CO2
injection, or VHO lighting, or substrate heating, or laterite. If you
made it this far, you're probably one of those folks that just
can't learn enough about this stuff. :-) Use your Web
browser to check out the aquatic plants section of the Krib at
HTTP://www.cco.caltech.edu/~aquaria
Tim Mullins - Pittsburgh
If you spot mistakes or have comments, please post or e-mail