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EI dosing question

990 Views 5 Replies 5 Participants Last post by  Zorfox
Im looking into mixing up some dry ferts to start the EI method for fertilizing my 45 gallon tank. Im currently running high light and Co2. While using the online calculators on here I noticed that there is The Estimative Index option and the EI daily one. Does anyone know the difference between the two and which one should I follow? I just want to make sure its the right mixture for the 500l bottle.
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· Premium Member
1,531 Posts
I don't know which calculator you are using, but the math is pretty simple if you know how much you want to dose each week. Looking at the size of tank you have, your weekly dosing would be
+/- 1/2 tsp KN03 3x a week
+/- 1/8 tsp KH2P04 3x a week
+/- 1/8 tsp Trace Elements 3x a week

Decide how much ferts you are going to add to your 500ml bottle. E.g. if you add 3 tsp of KNO3 your solution will provide 6 servings (two weeks) of nitrates. It's up to you how dense you want to make your solutions. Personally, unless you are using an autodoser (like a peristaltic pump) I don't think you should worry about mixing ferts up. Just add them to your tank and call it good.

· Registered
18 Posts
Thanks for the info. I used this one and got confused on different methods of how much to add for the mixture. Do I still need to worry about using the K2SO4? I currently use the seachem equilibrium to mix in my RO water for the GH.

I use that calculator too and dose EI daily. What I like to do is look at it from the view of how much of each fert do you want to dose in ppm over the whole week. To do this just multiply the daily dose by 7 or the EI dose by 3. You still enter the aquarium volume, however the ppm being dosed is always the same regardless of volume, only the amounts of ferts used changes in the calculator.

By playing with the calculator you can see that when you compare the 'EI Daily' method with the 'Estimative Index' method that the weekly values of ppm ferts are identical (based on 3x a week using EI). Once you figure out how much you like to dose for your setup I like to use the 'What Dose to Reach Target' method.

I believe Tom Barr's max recommended total weekly dosing for a high light, CO2 injected, heavily planted tank is about 30 ppm KNO3, 10 ppm KH2PO4, and 1.4 Traces (or CSM+B). Again this is how much you are dosing and not the values in the aquarium at the end of the week. My water is moderately hard so I do not dose K2SO4.

· Registered
357 Posts
Equilibrium provides potassium, no? If it provides enough for you, then you wouldn't need to dose K2SO4.
But honestly if you're using RO water, why not just dry dose the GH booster mix which will take care of both the GH and potassium?

· Registered
2,105 Posts
"The Estimative Index" selection is for classic EI dosing which is macros and micros on alternating days i.e...

Mon Macros
Tues Micros
Wed Macros
Thurs Micros
Fri Macros
Sat Micros
Sun 50% water change (no dosing except for GH alterations)

Typical macros and micros are...
Macros = KNO3 & KH2PO4
Micros = Plantex CSM + B

EI Daily is simply dosing everyday

There's generally enough potassium (K) in the KNO3 and KH2PO4. If you crunch the numbers,
A Full EI dose of K is 7.5ppm.
KNO3 & KH2PO4 adds 5.27ppm
This leaves a deficit of only 2.23ppm of K.

That's a weekly deficit (if you want full EI dose) of 6.69ppm of K.

One teaspoon of Seachem Equilibrium provides 6.10 ppm of K which would account for the extra K needed. I would assume you are adding more than this to reconstitute your R/O anyway. Make sense?
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