[StevenPituch]

Hi All,
I'd appreciate if someone could check my math. I want to determine the PPM of NO3 per drop of PMDD that goes in say a 10 gallon tank.

weight of one tablespoon of KNO3 = 15.8 gm
Percent NO3 in KNO3 = 61%
weight of NO3 in one tablespoon of KNO3 = 9.6 gm
drops in 500 ml of solution = 20 x 500 = 10,000
weight of NO3 in one drop of PMDD = 9600 mg/10000 = .96 mg/drop
10 gal tank is 3.785 x 10 = 37.85 liters
.96 mg/37.85 liters = .025 mg/l = .025 ppm

The reason I question this is a normal dose of NO3, I'm guessing, would be 5 or 10 ppm, but the recommended dose for a ten gallon tank is two drops or .05 PPM. Even if you triple the KNO3 in the PMDD as recommended, it is still a lot less than 5 ppm. So somewhere I must be mistaken. Any advice is appreciated.

Regards,
Steve Pituch

 

[mistergreen]

This calculator could help
https://rotalabutterfly.com/nutrient-calculator.php

 

[StevenPituch]

Yes, I saw that, but couldn’t figure out the inputs. There’s got to be a logical way to just do the math. My brain is getting old. ;o)
Steve

 

[StevenPituch]

I guess not many use PMDD anymore.....
Here is what I figured out. It may not be correct. I am using the PMDD formula from "The Krib".
-----------------------
Fe
Find dose of PMDD to give .1ppm Fe in 10 gallons of water:
1 Tablespoon of CSM+B (9 gm) equals 6.53 % Fe = (.59 gm Fe)
In 500 ml that’s 590 mg/.5L = 1180 mg/L = 1180 ppm
1180/20000 = .059 mg Fe/drop
Want .1 ppm solution in 10 gallons
(.1 mg/L) x (3.784L/1 Gal) x 10 Gal = 3.785 mg Fe
3.785/.059 = 64 drops = 3.2 ml PPMD will give you .1 ppm Fe in 10 gallons
-----------------------------------
NO3
There are 9.6 gm NO3 in 500 ml of PPMD. In 3.2 ml PPMD there are 30.7 mg of NO3.
30.7 mg NO3/ (10 x 3.785) = .811mg/L = .811 ppm
---------------------------------------------
Therefore add 2 more tablespoons of KNO3 to PPMD, as recommended by The Krib, and then the ratio will be .811 x 3 =2.4 ppm NO3 to .1 ppm Fe. Then I would dose 6 ml of PPMD per 10 gallons per day, which gives .19 ppm Fe and 4.5 ppm NO3.

 

[mistergreen]

I'm following PMDD sort of but I just drop the ferts straight into the tank and not make a solution.

 

[StevenPituch]

I'm following PMDD sort of but I just drop the ferts straight into the tank and not make a solution.

Yes, I think that's the latest way of doing it. But I was really into PMDD at the turn of the century, and after a lapse, I'm trying to figure it out all over again. Two things I've learned so far: 1) there are 20 drops to a ml, and 2) mg/L=ppm.

Steve

 

[hoppycalif]

Yes, I think that's the latest way of doing it. But I was really into PMDD at the turn of the century, and after a lapse, I'm trying to figure it out all over again. Two things I've learned so far: 1) there are 20 drops to a ml, and 2) mg/L=ppm.

Steve

mg/L only equals ppm when the liter is of water. So, the "formula" should be mg per liter of water - a liter of water has a mass of 1000 grams or 1,000,000 mg.