how do you use greg watsons pmdd pre-mix - Fertilizing

Marcom1234 · 09-09-2006, 11:23 AM

i would like to buy the greg watson pmdd premix... how do i use it? if i follow the EI method the different ferts are used in different quantities. so how much do i use if i assume that the ratios in the premix are correct?

i have a 20 gallon tank with no fish yet ... no plants yet either.. but i want to have the ferts on hand and a degree of knowledge before i buy the plants.
but i plan on getting aquabotanics hard to kill assortment for 20 gallon tanks...

i will be using DIY co2 for now.. and i have 65 watts of CF lighting a coralife colormax/6700 bulb. and laterite/normal gravel mix for substrate.

ok hope i gave enough info.

John N. · 09-09-2006, 06:36 PM

Marcom, it's actually best to dose individual fertilizers for greater control over the tank, especially if you are doing EI.

Do take a look at this thread . This thread is another justify reasoning. I'm not sure why Greg watson still sells this premix, but you'll need more then the premix. I'll have to look into dosing premix accordingly to EI if you are keen in doing it this way.

-John N.

Marcom1234 · 09-09-2006, 08:29 PM

well i guess the reasoning behind it was that i could buy one lb of the whole shebang instead of one lb of each different fert.

that would cost me almost 30 bucks instead of 9 buck.... plus would take up less room and so forth.

John N. · 09-10-2006, 10:53 AM

Marcom, I understand where you're coming from. I too thought that before I bought my first order of Gregwatson chemicals. However, ever since I bought the individual components, and found out by experience that they last for a extended period of time (1-2+ years) of daily dosing on several tanks, the intitial investment of $30 to control the ratios of dosing was well worth it.

PMDD premix simply isn't as useful in today's standard of High light tanks (3+ wpg) since it's better to dose individual chemicals. However, to answer your question, I would dose the Premix at 1/16 - 1/4 tsp twice a week (afterwater change, and then midweek). On the other days add 1/16 of K2PO4 to add the missing phosphate 2x per week.

This should give you a base line to start. If you see poor growth in plants, you'll need to increase the the premix dosage.

-John N.

hoppycalif · 09-10-2006, 11:19 AM

Since a quarter tsp of Greg's PMDD contains only 1/16 tsp of KNO3, I would add an equal amount of KNO3 to every dose of PMDD, then on alternate days dose about 1/4 of that PMDD dose in KH2PO4. In other words, for a 20 gallon tank, heavily planted, with high light intensity, I would dose:
1/4 tsp PMDD
1/4 tsp KNO3
and on alternate days
1/16 tsp KH2PO4
all dosed dry - just sprinkle in in the tank. (or, mix in a cup of tank water, then dump that in the tank.)
If the tank isn't heavily planted or if the light intensity is only moderate, I would dose those amounts twice a week.

PMDD contains only as much KNO3 as it does CSM+B, which would leave the tank starved of nitrates if you don't dose nitrates separately. And, of course, it contains no phosphates at all.

AndyT. · 09-10-2006, 11:36 AM

If it makes you feel any better Marcom, I purchased the premix before doing my homework... after it arrived I realized my mistake. Since then I have gotten the KNO3 and KHPO4 and rigged up a dosing schedule so that I do use up the PMDD pre-mix.

But looking at the various ways of fertilization which have popular currency today I don't even see why Greg offers the pre-mix...

I go with everyone else. Get the chemicals separately, dose them separately.