yet another EI dosing thread. - The Planted Tank Forum
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post #1 of 2 (permalink) Old 10-01-2018, 05:28 PM Thread Starter
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Question yet another EI dosing thread.


So I finally got my dry ferts from AFP (starter kit). A quick overlook at the guide (just looking at PO4):

1tsp Potassium Phosphate in 500ml Water.
Macro 3x a week. (10ml per 50ltr of Aquarium water)

So in a week that's 30 mL per 50L aqarium water.

My tank is 350L, so total should be 210 mL Macro per week.

As their quick guide explains:
'Typical Ei values will be;
Nitrate (NO3) 20ppm (parts per million) per week
Potassium (K) 30ppm per week
Phosphate (PO4) 3ppm per week
Magnesium (Mg) 10ppm per week
Iron (Fe) 0.5ppm per week'

However, checking the above values at rotalabutterfly calculator, ( I'm getting different values:

To reach your target of 4.7ppm PO4 you will need to add 5.61 grams (equivalent to 1 tsp) of KH2PO4 to your 500mL dosing container. Add 210mL of that mix to your 350L aquarium to yield:..

From James' planted tank calculator ( James' Planted Tank - Dosing Calculator), I get 5.53 ppm Phosphate from the same dosing.

So I'm somewhere between 3ppm and 5,5 ppm. That's quite a difference.

Which of the calculations are right? (if any)
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post #2 of 2 (permalink) Old 10-01-2018, 06:32 PM
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Just voicing interest in the topic. Can't claim to be an authority.

I've seen the same thing. As far as I can tell the advice on PO4 has evolved over the last few years and generally now higher levels/ratios are advocated. Back when I kept a tank just a few years ago the general consensus was 10:1 NO3:PO4 in ppm. Now it seems to be closer to 5:1 with the caveat that higher levels of PO4 are OK so long as CO2 is monitored and it doesn't drop as a consequence of increased CO2 uptake due to the increased PO4.

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