Measuring added fertilizers electronically


Newly Registered
18 Nov 2009
Uddevalla, Sweden

How is the level of fertilizer controlled electronically?

I read in Tropicas site this info: "The nutrition content of the water is monitored and dosed electronically to ensure that the fertiliser balance remains constant."

It would be interesting to be able to monitor this in a graph on my computer by using a conductivity probe.
Am I right, if I assume it's the conductivity that is measured, since the fertilizers added are salts they would impact on
the conductivity? And that the conductivity will be affected by waterchange, gravel material, evaporation and fertilizing. If the influence of the three first ones are known, the value for the fertilizer may be estimated?
It is basically the "half life expectancy" I am looking for.

Or is there any other ways to better measure levels of fertilizers in water?
(exept algae blooms :woot: )

Best Regards Leif


Expert/Global Moderator
Staff member
11 Jul 2007
Chicago, USA
Well, unfortunately, that's the one thing on the Tropica site that I wish you would not have read. In my experience, you don't need to measure the nutrient levels in the tank. As you should have read in the EI dry salt dosing tutorial, if you are dosing per the instructions, then you already have a very good idea of what the nutrient levels are. If there are nutrients in your water supply then this is even better and it may enable you to lower the dosing rates, but changes to the dosage rates should not be based on measurements. They should be based strictly on your observations of the growth performance in relation to your goals and objectives. If you want to maximize growth rates then keep adding more nutrients and CO2. If you want to lower the amount of maintenance then slowly reduce the dosing and CO2 levels. Furthermore, even if you could measure exactly the level of nutrient in your tank, this may mean nothing, because of all the other variables in the tank. So 20ppm NO3 in your tank may not have exactly the same effect as 20ppm of NO3 in someone else's tank. If you add more light for example to your particular tank you may find that 20ppm of NO3 is insufficient. Always keep in mind that there is no magic number for nutrient levels. The levels are only relevant when considered in context of all the other technical and social variables.

Conductivity is only a measurement of the total amount of solutes in the water, so it cannot, by itself tell you anything about specific nutrient levels. All you can conclude is that the more nutrients you add, the higher the conductivity will rise. Other than that, unless you are breeding fish or have some other goal in mind regarding the level of solutes there is not much relevance in this measurement.

I would strongly suggest that you study the following threads, some of which discuss issues many times more important than measuring nutrient levels, which I consider, quite frankly, to be not worth the energy:
Why dont nutrients cause algae?
Good Algae Article
Stable CO2 - What does it mean exactly?
Water flow in the planted aquarium

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