Some Help with modifying my dosing regimen.


Prolific Poster
Mar 31, 2008
Hi guys,

I am dosing E.I in my 145 liter planted tank. 1.4 grams of potassium nitrate 0.3 grams of potassium di hydrogen phosphate and 0.7 grams of potassium sulphate as dry powders on monday, wed, fri and Sun while i add 5ml of seachem flourish on tue, thurs and saturday.

My aquarium has been flooded for 3 weeks now and i have been performing a near total water change on wed and another 50 percent water change on sunday so as to make sure that algae doent take a hold during the initial weeks.

Now i dawned on me that i may be underdosing.. Plants seem to be doing well but should i double the doses in view that i do two water changes a week?? and EI only takes into account one 50 percent water change. I would like to keep the two water changes however i ll decrease the wednesday one to a 50 percent water change.

COuld you guys please tweak my current dosage regimen or should i leave it as it is??

Any help is appreciated.

Thanks a lot


Lifetime Charter Member
Lifetime Member
Mar 12, 2009
There's no absolute need to increase.

If you're dosing 20ppm NO3 per week because your plants are taking up say 16ppm a week, then 8ppm would be the uptake in 1/2 of a week so the required level dosed would only need to be 10ppm.

At the same time though you could increase to double so that you've got a much wider margin of error. Even dosing an extra 50% would leave you with a better padded system than EI typically provides, which is still pretty generous. Still, the general principle of EI is to take the wider path unless there's a concrete reason not to.


Guru Class Expert
Mar 5, 2009
I really think your dosing of NO3 is too low. Adding only 5ppm 4x/week NO3 is too low. I dose more on my low light tanks/slow growing plants. So, if you have higher light/fast growing plants, it will be very low NO3 on a starting tank with those WC

After the total near 100% waterchange, I'll dose the full need for plants: around 15ppm NO3, 1.5-2ppm PO4 and micro dose. K2SO4 could or not be dosed as you like, target 5-10 ppm after complete WC. If you increase NO3 as I propose (3.6g after complete WC), you won't need dosing K2SO4 as you'll be at 10ppm K with only dosing KH2PO4 and KNO3.

On the other hand, if you continue adding only 5 ppm after +80% WC, you could end up with too low NO3 between 2 doses. Let's say if after complete WC your remaining NO3 is 3ppm, you add 5ppm --> 8ppm. Plants will consume it and before next dosing you'll be lower than 5ppm. Even adding 5ppm at that day you'll be always surfing on the