Question on dosage amounts for EI method - The Planted Tank Forum
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post #1 of 3 (permalink) Old 12-14-2006, 09:38 PM Thread Starter
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Question on dosage amounts for EI method

Just read up on the EI method of fertilzing... my tank is a 30 gallon, and I'm curious at the popular suggested dosing regime for 20-40 gallon ganks:

20-40 Gallon Aquariums
+/- tsp KN03 3x a week
+/- 1/16 tsp KH2P04 3x a week
+/- 1/16 tsp (5ml) Trace Elements 3x a week
50% weekly water change

This is an example, but I've seen it on numerous sites (including this one). If the target levels for nutrients are:

CO2 range 25-35ppm
NO3 range 5-30ppm
K+ range 10-30ppm
PO4 range 1.0-3.0 ppm
Fe 0.2-0.5ppm or higher (?)
GH range 3 degrees ~ 50ppm or higher

Then if I use the Fertilator or Chuck's calculator to figure out how much I am dosing each week, at 3x a week it comes to:

7.02 ppm NO3 3x a week = 21.06 ppm
2.15 ppm PO4 3x a week = 6.45 ppm
5.31 ppm K 3x a week = 15.93 ppm
0.09 ppm Fe 3x a week = 0.27 ppm

Then.. under the assumption that the maximum nutrient levels you will have with weekly water changes is 2x what you are dosing... assuming, for the moment, that my tank has 0% uptake, at the end of the week I could potentially have:

42 ppm NO3
13 ppm PO4
32 ppm K
0.6 ppm Fe

Ok, so everything is pretty much in line with the target levels... a little higher, assuming some uptake I presume. Except PO4... 13 ppm where the target is 1-3 ppm?? Just trying to grasp this all before I start using it. Am I understanding things right?
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post #2 of 3 (permalink) Old 12-14-2006, 09:49 PM
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MMM, I know very little on the topic, but if you take N03 as the example:
Week 1: 3 * 7 ppm = 21 ppm

Waterchange of 50% with 0 uptake = 10.5 ppm

Week 2: 3 * 7 ppm - 21 ppm

Remainder from week 1 = 10.5 ppm
Week 2 dosage = 21.0 ppm
Total = 31.5 ppm with no uptake the second before the H20 change.

Bottom line, take all your results and multiply them by the following to determine your max possible concentration after two weeks:

0.86 for 25% weekly changes.
0.75 for 50% weekly changes
0.62 for 75% weekly changes

You need to account for the water change removing 1/2 of what you put in each week. Further more, I think you should be calculating an estimated minimum concentration if you want to follow Tom's EI method.
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post #3 of 3 (permalink) Old 12-16-2006, 06:49 PM Thread Starter
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Aye... I appreciate the comment kuhli, but you admit you are no expert. Does an expert have the same thoughts?
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