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> From: Jorge Q 
> Subject: PMDD Formula ?
> I'm about to mix up my first batch of homemade
> PMDD. I'm a little confused...Looking at the
> recipe, it states, "Pour in additional water to
> make 300 mL solution". Does this mean I use 300
> ml of water in total, or that I keep adding
> water until I have 300 mL of PMDD. Thanks...

You can use the recipe by adding a little water to mix it(generally does not
dissolve that well) first, say 100mls, then top it off for 300mls total. It
really does not matter that much if you add the liquid and top off to this
level vs adding the dry mix to 300mls of water, the slight difference will not
make or break a tank and the method suggest testing the NO3 and Fe, both of
which are pesky test IMO to measure uptake unless you have a nice NO3
kit(Lamott). I will not attempt to discuss Fe since I've gone into it prior. 

Adding it to 300mls of water vs bringing the level up to 300mls will change
the volume and hence the concentration since the dry salts will displace the
water giving a bit more solution and less concentration. But not that much to
effect a plant tank. I would not worry much about it. 

As far as a all in one mix:
I've never liked this but some folks like the simple aspect of adding one
liquid into their tank. I'm not around enough to add stuff every day nor wish
to be tied down to that routine, I like to go places for the weekend:-)

I always add K2SO4 dry. You will find it difficult to dissolve unless you have
very fine powdered grain sizes.

PMDD generally does not add enough traces nor K IMO.

Some folks have NO3 in their tap water, then PMDD does not work well for that

I'd rather add things dry, it's less messy, last forever, no issues with
dissolving the salts and you can get to within 1ppm using dry weight/volumes
with the macro nutrients.
Less solution base mixing, it's easier to measure 1/4 teaspoon than 5mls and I
don't have to mix a thing. 

The only thing I add liquid are traces. They come liquid or you can use the
CMS plantex etc and make your own.

I use 2 tablespoons added to 500mls/ 1/2 liter of DI water.

I add K2SO4 once a wek after a water change only.
PO4 is added every 2-3 days
KNO3 is added every 2-3 days
Traces are added every 2-3 days.

4 things, pretty easy.
No chemical background needed.

Some observational skills are needed to fine tune this but generally with
2-3w/gal, adding per 20 gallons: 1/4 teaspoon dry of KNO3 every 2-3 days
3-5mls of traces every 2-3 days, a smig of PO4(a couple of rice grain's worth
etc every 2-3 days, and add 1/4teaspoon or slightly more of K2SO4 after your
water change only.
Do 50% weekly water changes.
Be certain you have good CO2 levels, 20-30ppm at all times when the lights are

You'll find this to work quite well.......
....unless you have less light, very few plants, need to clean, scrub and trim
the tank prior to doing this etc.

You might consider getting some Flouish or Flourish Trace to add a few odd
taces(eg Boron) that are lacking in Plantex etc and add that once a week in
place of the plantex. 

It's simple, cheap and if you can make a batch of cookies from scratch, you
have the equipment and skill to do this.

The rest is pruning, adding herbivores, cleaning the filter and feeding the
fish etc.

The HOW is pretty simple and is old hat after a couple of times.

Tom Barr