Comparison of Seachem's Macro Ferts to Rex's Dry Macro Ferts

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Check this out. You might be surprised.

1 pound of dry fert = x liters of Seachem's ferts
1 lb of KNO3 = 3.7 L of F. Nitrogen
1 lb of K2SO4 = 4.5 L of F. Potassium
1 lb of KH2PO4 = 67.0 L of F. Phosphorus

Rex's price of 1 pound of dry ferts compared to DrsFosterSmith.com regular price of $26 for 2 liter jugs of Seachem's ferts
1 lb of KNO3 costs $2 = $48.10 of F. Nitrogen
1 lb of K2SO4 costs $2 = $58.50 of F. Potassium
1 lb of KH2PO4 costs $3 = $871.00 of F. Phosphorus

The price of 3 lbs of Rex's ferts is $7 and the 75.2 liters of Seachem's ferts price is $977.60.

You can buy 140 lbs of Rex's dry ferts for the price of these Seachem's ferts.

I never realized that Seachem's ferts are this expensive. I've read about people claiming that F. Potassium is a weak solution, but I never realized that F. Phosphorus is so weak. I went to Seachem's site to double check on the calculators. I came up with the same amounts that are shown in Seachem's dosing directions for each of these products.

I used Chuck's fert calculator and the fertfriend calculator to arrive at the equivalent ppm amounts of Seachem's ferts needed to equal the ppm that 454 grams of the dry ferts yield.

I used Chuck's calculator to find the ppm of 454 grams of the three dry ferts in 100 liters of water. Then I used the fertfriend calculator to find out how many liters of Seachem's ferts that it takes to equal this same ppm.

- 454 grams of KNO3 in 100 L yields 2785 ppm of NO3 that is equivalent to 3.7 L of F. Nitrogen.
- 454 grams of K2SO4 in 100 L yields 2040 ppm of K that is equivalent to 4.5 L of F. Potassium.
- 454 grams of KH2PO4 in 100 L yields 3170 ppm of PO4 which is equivalent to 67.0 L of F. Phosphorus.

Here's a little bit more about the calculations. This is Seachem's dosing directions results from their web site compared with the fertfriend results to determine it's accuracy. You can see that it is pretty accurate.

- F. Nitrogen: "DIRECTIONS: BEGINNER: Use 2.5 mL (half a cap) for each 160 L (40 gallons)...EXPERT: The beginner dose raises nitrogen by the same degree that 1 mg/L nitrate would." The fertfriend calculates 1.2 mg/L for 2.5 mL in 160 L.

- F. Potassium: "DIRECTIONS: Use 1 capful (5 mL) for every 125 L (30 gallons). This dose raises potassium by 2 mg/L." The fertfriend calculates 1.8 mg/L for 5 mL in
125 L.

- F. Phosphorus: "DIRECTIONS: BEGINNER: Use 2.5 mL (half a cap) for each 80 L (20 gallons)...EXPERT: The beginner dose raises phosphorus by 0.05 mg/L
(0.15 mg/L phosphate)." The fertfriend calculates 0.15 mg/L for 2.5 mL in 80 L.

You can see the fertfriend is fairly accurate. You have this...
- F. Nitrogen: 1 mg/L vs. 1.2 mg/L - NO3
- F. Potassium: 2 mg/L vs. 1.8 mg/L - K
- F. Phosphorus: 0.15 mg/L vs. 0.15 mg/L - PO4

(I rounded my calculations to one decimal place for simplicity.)

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[wkndracer]

With the high cost differential between the two and after fully reviewing the facts only a government procurement agent would continue to purchase water over the dry chemicals.