# PMDD (Poor Man Dupla Drops)



## Plant Crazy

Some of you have been asking for more information about PMDD for fertilizing your plants. PMDD, short for 'Poor Man Dupla drops', was originally conceived as a cheap substitute for Dupla liquid fertilizer. PMDD contains all the necessary macronutrients (with the exception of phosphorous) and micronutrients, including chelated iron. The reason it doesn't contain phosphorous, is that a series of experiments by Sears/Conlin in 1996 suggested that by limiting phosphate, we could control algae growth:
http://www.thekrib.com/Plants/Fertilizer/sears-conlin.html

However, thanks to observations from Tom Barr (a plant guru of many, many years), who has incidentally started his own website: http://www.barrreport.com/, we now believe that nutrient DEFICIENCIES as opposed to excess, result in algae blooms. Thus, we now strive to dose phosphate, as opposed to limit it, and aim to keep phosphate levels at 1 to 1.5 ppm.

The PMDD recipe that I use is located here: http://www.thekrib.com/Plants/Fertilizer/pmdd-tim.html
You can buy all the ingredients you need for PMDD at any Homegrown hydroponics location: http://www.hydroponics.com/info/aquatics/pmdd.htm NOTE: If you're located in the US, you can buy your ferts from Greg Watson.com: http://www.gregwatson.com/PMDDStoreInfo.htm

You need to buy 1- Potassium nitrate KN03 (to supply nitrate), 2- Potassium sulfate K2SO4 (to supply potassium), 3- Epson salts MgSO4+7H2O (to supply magnesium), 4- chelated trace mix (contains chelated iron as well as other micronutrients), 5- Monopotassium phosphate KH2PO4 (to supply phosphate).

Then mix up the PMDD according to the recipe (e.g., for 500 mL, add 1 tablespoon chelated trace + 1 tablespoon Epson salts + 2 tablespoons potassium sulfate + 1 tablespoon potassium nitrate), and store it in the fridge. I make up the monopotassium phosphate in a *separate bottle *and also store it in the fridge (4 tspn of KH2PO4 in 250 mL water; 1 mL of this adds 0.2 ppm phosphate). So you'll end up with a bottle of PMDD, and a bottle of phosphate.

Then, I measure my tank's NITRATE, and PHOSPHATE levels using the Aquarium Pharmaceuticals brand nitrate and phosphate kits. I then dose the PMDD and phosphate to your tank accordingly: I aim for a nitrate level of 5 to 10 ppm, and phosphate level of 1 to 1.5 ppm.

If your nitrate level is too high, then do water changes, feed your fish less, or remove some fish. If your nitrates remain high, you can also mix up some PMDD *WITHOUT*the potassium nitrate, and dose this into your tank. That's the advantage of mixing your own fertilizer mix; you can customize it according to your tank's needs.

If your nitrate level is too low, then dose PMDD to get the nitrate between 5 to 10 ppm. Note, if you have lots of lighting and CO2, your plants may be consuming lots of nitrate. In this situation, you can make some PMDD with double or triple the amount of potassium nitrate (e.g., 2 or 3 tablespoons of potassium nitrate per 500 mL, instead of 1 tablespoon).

If your phosphate level is too high, do the same suggestions as for high nitrates, and do NOT dose the phosphate until the levels of phosphate go below 1 ppm.

If your phosphate level is too low, dose enough phosphate to get it to 1 to 1.5 ppm.

By measuring your tank's nitrate and phosphate levels before and after the addition of PMDD and phosphate, you'll get an idea of how much you'll need to add to raise your tank's nitrate and phosphate by a given concentration.

So in summary, you'll be measuring NITRATE and PHOSPHATE levels. You'll be dosing PMDD to keep your NITRATE at 5 to 10 ppm. You'll be dosing phosphate to keep your PHOSPHATE at 1 to 1.5 ppm. The reason we don't measure POTASSIUM, is that excess potassium is not believed to cause algae outbreaks, and it is notoriously difficult to measure as well.

NOTE: If you are feeding your fish heavily (e.g., discus), you may find that your nitrate and phosphate levels are high, and thus do not require supplementation with nitrate and phosphate. However, you should still dose potassium (via K2SO4) to ensure that potassium won't become a limiting macronutrient. Although I can't absolutely confirm this, I believe that certain fish foods will increase your nitrate and phosphate levels, without substantially increasing your potassium, and thus this situation requires that you still dose potassium.

(Note: ppm is short form for 'parts per million'.)

There are many other ways of dosing fertilizers, however this is what I've found that works the best for me. There is also the 'Estimative Index' which you'll read about on other forums. It was devised by Tom Barr. This method does NOT rely on the use of test kits. It doses dry fertilizers (not premixed) directly into the aquarium, with macros and micros dosed on separate days. It also uses a 50% water change at the end of the week to 'reset' the tank. More info can be found at: http://www.barrreport.com/forums/showthread.php?t=1

Regardless of the method that you choose, mixing and dosing your own fertilizers has several advantages: it's VERY cheap, it allows you to dose an exact amount of macros, and allows for the dosing of macros separately. This last point is very important. For example, if your nitrate level is already high, by dosing an 'all-in-one' commercial plant fertilizer, you'd be adding more nitrate, along with the other macros and micros, which would promote algae growth. In this situation, you'd customize your PMDD mix so that nitrate would not be dosed.

A great summary of fertilizing and other aquatic plant tips can be found at: http://www.rexgrigg.com/./ferts.htm


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## jrs

That is a good post.

I didn't have K2SO4 so I substituted KCl for it and it seems to be working well.

jrs


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## ranmasatome

*Misuse of the term 'PMDD'*

Just as a side note...If you dose these elements separately in different amounts, like i do, please dont use the term PMDD.

As we all know and mentioned previously by plant crazy, PMDD stands for Poor Man's Dupla Drops. It was created in the earlier days of the planted tank hobby when commercial aquatic plant fertilisers were few and expensive. This much more affordable alternative was created from *loose fertilisers *(i.e. KNO3, K2SO4, MgSO4.7H2O, trace fertiliser mix) by Sears and Conlin, and they shared the recipe freely on the Internet. PMDD actually refers to *THAT VERY* mix of *loose fertilisers or inorganic fertilisers*
Unfortunately, the term PMDD has been misused to refer to the loose fertilisers/ inorganic fertilisers that many hobbyists dose separately nowadays. i dont think that is helpful because forums are good stores of information for the hobby and misuse of terms could lead to mis-information or inaccurate or frustrating information searching. Also, I feel we should respect the work done by these pioneers in the modern planted tank hobby and not misuse terms that refer to key or important outcomes of their efforts.

What i can think of to use right now would probably be.. 
- Chemical fertilisers
- Inorganic fertilisers
If anybody has a better idea, do post.


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## Plant Crazy

I'm still using the same amount of KNO3, K2SO4, MgSO4 and trace elements as Sears and Conlin recommended in their PMDD mix, thus I referred to it as 'PMDD'. I dose the PMDD nutrients all together. I know that some people will dose the KNO3, K2SO4, and traces separately, but I've found that dosing these together according to the PMDD recipe works quite well. 

I dose KH2PO4 separately (and this was not included in the PMDD mix, as Sears and Conlin believed from their pioneering work, that phosphate limitation was important for controlling algae growth).


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## ranmasatome

i know you do.. you mentioned it in the thread above mine..
Just a side not to others..


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## holocron

*outstanding thread stan.*

Thanks for posting this information Stan, it is absolutely vital information for any 'planted tanker'. A+++ post.

Personally I mix up 3 250 ml bottles of ferts. The first is just trace (and sometimes MgSO4) the second is K2PO4 (mono-potassium phosphate) and the third is KNO3 (potassium nitrate). I then dose the ferts based on the growth and algae in the tank. I do tests from time to time to verify my dose schedule, etc. I found that dosing NO3 and PO4 combined in my PMDD wasn't very efficient, as I found that I needed to put way more trace in my tank than nitrate and more phosphate than nitrate. I had to many fish in my tank so the nitrate was always high (until recently when I sold many fish).

I did start with PMDD and then moved to a more 'controlled' fert scenario. I am thinking of trying Tom Barr's method next to see if the routine will provide the best case for growth.

thanks again, I have given you *2* more ballots in the discus draw.


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## Plant Crazy

Just to remind everyone (including myself), that keeping your tank's parameters at optimal levels will still NOT guarantee an 'algae free' tank. 

Although using PMDD, or individually dosing your ferts can help swing things towards an 'algae free' tank, there are other factors to keep in mind:

- Keeping your CO2 levels at 30 ppm
- Having enough fast growing plants
- Keeping your bioload low and not overfeeding
- Maintaining a light cycle of ideally 10 hr or less

Even with optimal water parameters, I'm having to deal with thread algae in my new planted discus tank, likely due to the bioload, heavy feedings required, and removal of some fast growing stem plants (rotala indica, star gras). I guess if planted tanks never had algae outbreaks, then where would the challenge be?


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## jrs

Bingo!

The threat of algae, plants dying or not growing well and the higher maintenance is what makes the planted takes much more challenging.


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## ranmasatome

Plant Crazy said:


> - Keeping your CO2 levels at 30 ppm
> - Having enough fast growing plants
> - Keeping your bioload low and not overfeeding
> - Maintaining a light cycle of ideally 10 hr or less


take note there the word is "keeping" and not "hitting"...consistancy is key.
Fast growing plants aren't exactly essential..when the tank is matured.. plant mass is more critical.. even if its a whole big bunch of slow growing plants...its good.
You can also slow the system down to get less algae.


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## kwonger81

holocron said:


> I found that dosing NO3 and PO4 combined in my PMDD wasn't very efficient, as I found that I needed to put way more trace in my tank than nitrate and more phosphate than nitrate. I had to many fish in my tank so the nitrate was always high (until recently when I sold many fish).


Thanks for posting this info on PMDD, Stan!! When it comes to planted tanks you are a Jedi Master and I your Padawan!

One question for Holo - how do you know if your traces are low? In your post, you said that you need to put more trace than nitrate - are you saying that based on the high nitrates? (and assuming that the nitrates are from the fish waste and not from too much ferts?) I think I may have the opposite problem, if that's possible.

In my 30G, currently stocked with a 2.5" clown loach, 1 rummynose tetra, 1 harlequin rasbora, 3 1.5" BN plecos, 2 oto cats, 12 small guppies (av 0.5"), and 10 Amano shrimp (just added over the weekend), every time I check my nitrates, they are 0 ppm. I'll then put in 1 cc of Stan's PMDD (he was nice enough to give me some to start off), and it will go to 5 ppm. So in situation, do I assume that if the nitrates are low, then the traces are low too?

FYI, lighting (Stan's old Coralife power compacts) is at about 3 wpg and I leave them on for around 12 hours - I will be cutting back to 10 hours starting tonight. Using 2 Hagen CO2 injectors. I finally got my pH down to 6.8 this morning (before I never had it below 7.0), so with a KH of 7, I finally achieved a CO2 level of 33 ppm!

I've got relatively small amounts of a few different types of algae going on at the moment. I'm going to try to achieve nutrient, CO2 etc. equilibrium before I try anything drastic (I started by getting those Amanos and I'm hoping to get some cherry reds in the next week or so - they're so expensive at BAs!). I'm guessing that total eradication is a bit of a pipe dream.


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## ranmasatome

For most co2 tanks.. priority goes..

1)This is the NO.1 Problem...get your co2 correct...You need consistant co2 throughout the day. If your co2 fluctuates.. you may end up with a BBA problem. Measure your Co2 throughout the day.. you should hit 30ppm within an hour your co2 switches on.. and then it should maintain this rate until it switches off.. this means that no matter when you measure (you should at least measure multiple times thoughout the day to be sure, i do it 5 times in a day for one day to be sure).. it should be at 25-30ppm.

2) Macro nutrients... get them to the right ppm for your tank. There are suggested concentrations depending on the method you choose to follow.

3) lastly.. micronutrients or traces... because they are needed in very little amounts.. they come last..but they are still important.

i personally choose not to go PMDD because dosing separately gives me more flexibility.


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## kwonger81

ranmasatome said:


> For most co2 tanks.. priority goes..
> 
> 1)This is the NO.1 Problem...get your co2 correct...You need consistant co2 throughout the day. If your co2 fluctuates.. you may end up with a BBA problem. Measure your Co2 throughout the day.. you should hit 30ppm within an hour your co2 switches on.. and then it should maintain this rate until it switches off.. this means that no matter when you measure (you should at least measure multiple times thoughout the day to be sure, i do it 5 times in a day for one day to be sure).. it should be at 25-30ppm.


Unfortunately I am using yeast CO2, so I am guessing that my CO2 levels are fluctuating (greatest by the morning before my lights go on, lowest at the time my lights go off). I've tried the CO2 twice a day once before (it went from 18 in the morning to 11 at night). I will try measuring it more times during a day perhaps this weekend.


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## Plant Crazy

Hey Jeff,

First of all, I can hardly be considered a Jedi. Veterans in the field like Tom Barr, Rex Grigg, Karen Randall, Diana Walstad, Chuck Gadd and many other notables are the true 'Jedi'. I'd be lucky to even call myself a Jedi in training. I feel comfortable maintaining my water parameters in a low bioload tank, however now with my discus planted tank (the little piggies!), I'm back at square one... a new struggle against algae. Also, my aquascaping sucks... perhaps one day I'll be able to sculpt creations like Takashi Amano. It's all a process. First, trying to get plants to grow well, and algae free, then trying to go for a beautifully arranged aquascape.

Ranmastome has made some great pointers. Keeping CO2 levels *consistently* elevated is important for keeping certain types of algae (most notably, BBA) at bay. I had problems with BBA before when I was using yeast CO2. However, once I went pressurized CO2, and was able to keep consistent CO2 levels, BBA was no longer a problem. If your BBA gets out of control, you can consider trying the Flourish Excel overdose method. As well, the amount of nitrate to trace in the PMDD mix you have should be providing adequate amounts of trace to your tank. As well, if you are able to add the PMDD daily, you'll be providing fresh trace (importantly, chelated iron) on a daily basis. Some people have advocated the measurement of chelated iron concentration as a surrogate for trace element levels (ie., if your iron is 0.1 to 0.2 ppm, then you have sufficient trace elements). I have used the Hagen Iron test kit in the past, and it works well for this purpose. However, I no longer measure Fe levels, as I observed that my trace elements were never deficient when I was dosing with sufficient PMDD. As ranmastome mentioned, it's the macros that you'll usually be deficient in, as opposed to the micros. As well, you can often physically observe plant changes that suggest certain trace element deficiencies: http://www.csd.net/%7Ecgadd/aqua/art_plant_nutrient.htm

By the way, if you want to see some beautifully aquascaped creations with lush plant growth, check out Ranmastome's journals!

Keep us updated with the progress of your planted tank.

PS- Harold usually stocks cherry red shrimp at the Menagerie (just call beforehand and check to see if they're in stock). Great prices too, especially if you buy 10 ($22?).


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## ranmasatome

Thanks for the compliments PC..
i'm taking photos of another tank soon. Will post once i get of my lazy A$$..haha..

10 Cherries for $22? okay..then i take back my earlier statment i made somewhere else about being cheap and lazy... then resort to dumping 100+ shrimp into your tank for algae control.. at least in Canada.. not advised..


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## Plant Crazy

No probs. Hey, with tanks like you've got, you deserve it. Good luck with the AGA 2006 competition.


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## Suzanne

I have found 2 different recipes for PMDD

500 ml (1/2 litre)
1 tbsp chelated trace 
1 tbsp epsom salt
2 tbsp potassium sulfate
1 tbsp potassium nitrate

or 

300 ml with distilled water
1 tbsp chelated trace 
2 tsp potassium sulfate
1 tsp potassium nitrate
2.5 tbsp epsom salts

Help! or are they both the same?


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## Zebrapl3co

I am more familiar with the 300 ml formulae.
But to be very honest, all planted tanks not being equal because it depends on how much plant you've go in the tank as well as what type of plants.
If you put in the time and patiences eventually you'll come to realize that you have to tweek the formalae a big to better suit your own tank.

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## Zebrapl3co

Bump for a good read. Supprisingly, I found this thread through google while searching for PMDD formula.
I do a search for PMDD mix and GTA was the first link. We came up on top of the Krib, plantedtank and plantgeek. Nice.

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## twoheadedfish

i'm sure you meant "bumped for great justice."

this IS a cool thread. thanks for bringing it to my attention.


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## Calmer

All this info is still very relevant and should be a sticky. I enjoyed reading this.
Great information


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