# Watson PMDD Pre-mix, no phosphate?



## David W. A. (Aug 22, 2006)

Contains 1 part Potassium Nitrate, 1 part Potassium Sulfate, 1 part Magnesium Sulfate, 1 part Plantex CSM+B.


why doesn't it have Phosphate too? I went to Greg Watson and bought the PMDD pre-mix, but wonder why monopotassium Phosphate isn't included?

I have a somewhat heavy fish load, lots of light and CO2 - I think I read somewhere that I might get all the phosphate I need from fish waste, so maybe I shouldn't care about phosphate?

David A.


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## bigstick120 (Mar 8, 2005)

Plants need PO4 to grow, its not in the PMDD mix because the CSB and PO4 will react and cause a white cloudy mess.


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## Adrian (Aug 4, 2006)

*No Phosphate*

The original Sears Conlin work pointed out to phosphate as the source for algae. It stated that for as long as you have your nutrients in check and low phosphate levels then algae will not be a problem. Later this has been proven not to be true (check some readings by Tom Barr on Estimative Index). I overdosed phosphates a few times to 10ppm and no algae infestation happened.

To answer whether you have enough phosphates - it depends on other nutrients, especially light. You can run a beautiful low tech tank with fairly low level of light and using only what the fish will provide as a fertilizer, or you can have plenty of light and fast growth but this requires other nutrients to follow - CO2, NPK and macro.

Hope this helps,

Adrian


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## David W. A. (Aug 22, 2006)

I think the underlying question is - do I need Phosphate? 

In another posting it was suggested that I do, but I wasn't keen enough to see that the PMDD mix from Watson didn't include Phosphate when I ordered it. Seems strange that if it is an important element why isn't in the mix - old issue or not. 

I have pressurized CO2, 4x65 watts on 120 gallons, with a moderately heavy fish load.

David A


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## hoppycalif (Apr 7, 2005)

When PMDD was developed it was the cutting edge for fertilizing, a way to fertilize and not spend a fortune on pre-mixed liquid fertilizers. At that time phosphate was considered to be something to be removed from the water, not added, and nitrate was considered to be just another trace element. So, PMDD contains too little nitrate and no phosphate. You could still use it, just as you could still drive a Ford Model A and get where you were going.

I suggest you treat a PMDD mix as a trace element mix and dose nitrates and phosphates separately.


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## David W. A. (Aug 22, 2006)

Hoppycalif,

I am starting to understand. I will get phosphate and nitrate. I think I will buy all the basic ferts in dry quantity and custom mix per the EI sticky and forgo the PMDD - it doesn't have the right parts (or ratios) to start. Wish I knew this before I purchase 4 lbs of it. 

Suggestion - The EI forum should have a sticky, or an addendum to a sticky that points out (Watson website could do a better job explaining this too) that the PMDD does not meet the EI dosing formula. Its seems clear now, but a week ago the PMDD seemed like a no brainer, everyone is doing the EI, Links to the GW website all over the place, here is ready to use premix with a bunch of big chemical names in it, must be good? but its missing 1 big fert and it isn't necessarily in the right ratio.

If I use the PMDD pre mix to get the 1-1/2 tsp dose of KN03, I will be adding the same 1-1/2 dose for the other ferts too, because the PMDD is equal parts. Although the EI allows for extra ferts with frequent and robust water changes - I guess this could be ok. Just seems like the PMDD is a bit off base. Maybe GW has a ton of it to sell? It isn't obvious to the newbie that the PMDD is not exactly the EI formula.

Disclaimer, I am not sure I am ready, i.e., knowledgeable enough, to really make all these assertions in earnest yet. I could easily still be missing something pretty big and obvious. So far, this is my take on things.

Your advise has been rock solid to the extent I have been able to understand it - how do you find the time to babysit all of us newbies - I appreciate your help. BTW, I like your avatar, it always makes me smile. 

Must do things fast, I have bubbles all over the place 

David W. A.


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## Bert H (Mar 2, 2004)

David, I can understand your confusion over the issues here. There's a lot of info to digest when you're first starting out in this hobby. One of the things to realize is that there are multiple ways to achieve the same effect. PMDD is indeed based on the Sears-Conlin belief (back in planted aquaria's 'dark ages') that phosphates caused algae. We now know better. Standing for 'Poor Man's Dupla Drops', it was intended to be dosed daily. Many folks still believe that daily dosing is better than EI. Both forms work, you just have to decide for yourself how you want to go. My guess would be that folks who use PMDD from Greg Watson, also dose phosphates separately.

Having had several dealings with Greg in the past, I can vouch for his customer service and integrity. I once asked for a small sample of one of his products to try out and he shipped me an entire order free of charge.


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## Jimbo205 (Feb 2, 2006)

> I once asked for a small sample of one of his products to try out and he shipped me an entire order free of charge.


 What a deal!

I was going to get some CSM+B and when I went to check out, the shipping charge was the same cost as the product. Luckily one of the other members just sold me a small batch for a decent price.

But I was thinking the same thing. 
I would love to order a 'sampler pack' from Greg. 
I figure with the shipping costs, it might actually more sense!

(And then later on I can figure out what ALL the EXTRA stuff he sells are for.)


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