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Daily vs Weekly Fert Dosing


10 Jun 2016
It is time to mix up a new batch of ferts which has lead to a few different articles and got me thinking.

One article started talking about the need to dose regularly to keep levels relatively consistent. Whilst I suspect this was written about high tech systems it did get me wondering if there is any difference between dosing daily rather than daily (other than ease).

So if you added say 10g of KNO3 in one after a water change vs say 2g a day each day for five days would there be any difference to the plants / inhabitants?

I am guessing that part of the EI daily dosing is the rate of usage and putting in the amount needed for a week would start to cause toxicity issues for plants / inhabitants?

I presume in a medium / low energy setup it doesn't make any difference?


15 Jan 2020
I'd always choose daily small doses of anything instead of massive weekly spikes. The same thing happens in nature - plants digest rather steady doses of nutrients and spikes are rare - massive amounts of ferts are usually pushed into the rivers/ground etc during wet periods and then they slowly deplete.


Global Moderator
25 Jan 2012
The reason you daily alternate dose macro and micro, as opposed to weekly, is that the macro's and micros if dosed together react and become plant unavailable. The potassium phosphate in the macro reacts with the iron chelate in the micro and precipitates out as plant unavailable iron phosphate.

IThus your plants, will eventually start showing signs on phosphate deficiency (stunted growth) and iron deficiency (pale new leaves). Normally it is iron deficiency shown, as generally there will be more phosphate in a dose than iron chelate, so some phosphate will remain once all the iron has precipitated out.


14 Mar 2018
According to Dennis Wong, there isn’t sufficient concentration of potassium phosphate and iron after dilution in the tank water to precipitate out each other. So if you dose macros at one end of the tank, wait for a few minutes of circulation and dose micros at the other end, there should be no interference. However, even chelated iron doesn’t last long in tank water before precipitating out as Fe3, so daily dosing of iron is beneficial to make it bio available to plants at all time. That said, plants can uptake iron in batches in time of plenty for use in lean time, so skipping some days without iron dosing may not necessarily be detrimental.

Certainly daily small dosing is better than weekly large dosing because plants prefer stable condition than large fluctuations similar to daily small water change is better than weekly large water change. However, unless one has a dosing machine, it’s impractical to do daily dosing for most people who have other life and what if one has to travel away from home for days.

What I do is a compromise. I do weekly large water change and macros micros dosing, followed by chelated iron dosing every other days. I have heavy bio load and feed my fish daily, which supplement N, P largely, and other nutrients daily from fish food. It’s working out for me based on observation of my plant health, but may not necessarily work out for set ups with low bioload as fish food supplement of nutrients may not be adequate.
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