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PMDD: Sources and Doses (tablespoon version)

Here's my updated post on where to buy PMDD (poor 
man's dosing drops) and how to use it. Many thanks
to those who have made comments and helped me along.

Note: In previous versions of this post I had my
PMDD mixed at 1/3 standard strength (I used teaspoons
instead of tablespoons in the mix). I've adjusted both
my recommended and historical dose levels to reflect
use of standard strength PMDD. Please excuse the repost;
I know APD space is valuable, but a number of people asked.
[Thanks to Steve Turner and Pat Bowerman for mix-fix]

Conlin and Sears' latest PMDD formula:
mix with water to make a 1/2 liter solution,
       1 tablespoon chelated trace mix
       1 tablespoon MgSO4+7H2O
       2 tablespoons K2SO4
       1 tablespoon KNO3  (more or less, depends on nitrate)

    [Thanks to Conlin and Sears who continue to
    experiment and refine their formula]

 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 a 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 have concerns with Cu (copper) being
      in a PMDD trace mix (Cu can be quite toxic to
      plants and fish in high concentrations). It is
      in Microplex and to a lesser extent in CSM. I
      haven't had any problems with CSM though I do
      change a lot of water each week. Many have had
      success with Microplex too. If you use some other
      trace formulation, you might want to be sure its
      Cu percent isn't too high.

 B)  Sources for MgSO4 (Magnesium Sulphate)
      and H3BO3 (Boric Acid)

 1)  MgSO4 is available from just about any drug
     store as Epsom Salts. $2 buys plenty. 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 used
     to supplement CSM (skip if your trace mix
     already has boron). Also available from drug
     stores, a couple buck buys around 250mG, a lot.
     [Thanks to Paul Sears]

 C)  Sources for KNO3 (Potassium Nitrate)
      and K2SO4 (Potassium Sulphate).

 1)  ECO Enterprises  1-800-426-6937
     1240 NE 175th Street, Seattle WA
           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
      [Thanks to Suwat Phruksawan & Louis Lin]

 D)  Source for complete pre-mixed PMDD per original
     Conlin and 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]

 E)  How 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.
     I've noticed it has no Co (cobalt) either, but I've
     not found the need to add any.

      To add B to CSM in a ratio of 5.5Fe (iron) to 1B
        - mix 10.5 teaspoons of CSM to 1 teaspoon of H3BO3
          (CSM+B works out to be 14 to 1 by weight).

      Here's the breakdown
        Regular CSM         CSM+B Mix
        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     0.0%            1.18%
        Co    0.0%            0.00%

 2)  So, using the Conlin and Sears PMDD formula:
      mix with water to make a 1/2 liter solution:
       1 tablespoon trace mix "CSM+B"
       1 tablespoon MgSO4+7H2O
       2 tablespoons K2SO4
       1 tablespoon KNO3 (more or less, depends on nitrate)

     Some mixing notes:
        - 1/2 liter is a lot of PMDD. You can easily mix 1/3
          as much by replacing "tablespoon" with "teaspoon"
          and mixing into 167ml of water (note: one tablespoon
          equals three teaspoons).
        - Don't make too much CSM into CSM+B. You may
          find later on you'll want to experiment with pure CSM.
        - 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 mix should be completely dissolved. Crush
          any undissolved crystals with your mixing tool.
        - To figure out whether to deviate from the 1 tablespoon
          of KNO3 suggestion, check part 4 of "How to Dose PMDD".
        - The KNO3 may have trouble becoming completely
          soluble and a fine particulate will settle out. That's
          ok, just shake the PMDD bottle before use.
        - Some recommend mixing 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>.

 E)  Why to consider rolling your own PMDD:

 1) True, there are many commercial aquatic plant
    fertilizer manufacturers like Seachem (Flourish),
    Dupla (DuplaPlant 24), Kent Marine (Freshwater Plant),
    Aquarium Products (Flora Boost), Coralife (Iron and 
    Micronutrient), Red Sea (AquaFlora), Tetra (FloraPride)
    Hawaiian Marine (Ferrovit), Jungle (Plant Saver),
    Wilken (FloraSan), Wiegandt (FerroPlant), Kordon 
    (Plant Nutrient), Aqualine Buschke (Ferreal and Floreal)
    Tropica (MasterGrow).

2) So why bother with PMDD when you can buy these?
    - Well. . . try them. If you find success at a reasonable
      price, great! And please, share your discoveries!
    - While requiring a bit of an initial outlay, PMDD is cheap
      over the long run (hence, PMDD: poor man's dosing drops).
    - PMDD tries 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 with element
      ratios and tailor it to meet your requirements.
    - It yields results comparable to some far more
      expensive brews.

 G)  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 will help:
      a) Put your PMDD in a dark brown or opaque
         bottle (I use well rinsed glass cough syrup
         bottles). Light can destablize chelates.
      b) I refrigerate my main stock (mark it well so
         someone doesn't take a swig) and leave a small
         25ml 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.

 H)  How to dose PMDD

     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 could be
     injurious to plants and fish.

 2)  As a starting point, for each ten gallons, try around 
     1/12 ml (milli-liter) of PMDD a day (roughly 2 drops).
     So, for a 29 gallon tank, start with 1/4 ml of PMDD a

     If you don't change much water, you might want to dose
     less. If you have a high tech, CO2 injected, VHO lit,
     heavily planted tank, you might want to dose a little
     more (still, I'd stay under a double dose at least until
     you get a number of weeks worth of feedback).

 3)  Many seem to recommend dosing PMDD to maintain
     around 0.1mG/ltr (0.1 milli-grams/liter or 0.1 Parts Per
     Million) concentration of Fe (Iron) in the aquarium and
     letting the other element concentrations fall where they
     may. Consensus seems to be 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 Fe deficiency or
     chlorosis (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 agreed 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. As time passes, you
     might notice 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 may need some KNO3, perhaps
     one to two tablespoons. Still, 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 waste.

     Most terrestrial plant fertilizer supplements have a lot
     of P. They may also have N in the form of NH3/NH4
     (ammonia/ammonium) or CO(NH2)2 (urea), both 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".

       Also, if you have a small aquarium and find
       fraction mL doses tough to dispense, you can dilute
       the PMDD and adjust dosages accordingly.

 I)  Some of my dosing experience

     Did I follow my own advice and go slow . . . no. <g>
     I initially dosed with 1.66 ml 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 1.66 ml dose), I reduced my
     PMDD dose to a little over 1/3 ml a day.

     My plant growth really improved.    :-)

 J) PMDD's breakdown by element:

       G/ltr    % total  Ratio to Fe
 N      4.24     6.41%    3.06
 K     41.40    62.53%   29.84
 S     15.56    23.50%   11.21
 Mg     2.86     4.32%    2.06
 Fe     1.39     2.10%    1.00
 Mn     0.40     0.60%    0.29
 Zn     0.08     0.12%    0.06
 Cu     0.02     0.03%    0.01
 Mo     0.01     0.01%    0.01
 B      0.25     0.38%    0.18
 Co     0.00     0.00%    0.00
 And two important quantities
 NO3   18.78     --      13.54
 SO4   46.67     --      33.63

 K) 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: 1.66ml PMDD, 45 gallon tank (40 gallon
    160 liter water column), and Fe is of interest.

     [(1.39G/ltr)*(1000mG/G)]*[(1.66ml)*(ltr/1000ml)]/(160ltr) =

         _0.0144 mG/ltr Fe_  increase in aquarium from 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 mG/ltr 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, aye?

     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)*(doses 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): 1.66 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

     Uh-oh, 4 times too high! That's why I ended up
     leveling off at a lower PMDD dose, about 1/3 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".

 L)  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

     Tim Mullins - Pittsburgh              tmullins at telerama_lm.com
     If you spot mistakes or have comments, please post or e-mail