Base ppm values for nutrients ???


New Member
Oct 6, 2021
I am struggeling and searching for this answer for a while. A lot of articles about EI regimes are prescribing dosage of nutrients based on the maximum uptake possible by plants under optimum circumstances. This seems logic to me. But i am wondering what the initial present concentration must be of nutrients as initial basis. This because i can inmagine that a certain minimum concentration must be present to support optimal plant growth. For example NO3 as source of N. Should there be a minimum level of 50 ppm present or is 10 ppm enough? The EI dosing regime is than meant for keeping this level approximately as is.
The same question for PO4, K, Mg and Ca?
I hope my question is clear...


Super Moderator
Staff member
Lifetime Member
Jun 20, 2016
CO2 range 25-35ppm
NO3 range 5-30ppm
K+ range 10-30ppm
PO4 range 1.0-3.0 ppm
Fe 0.2-0.5ppm or higher (?
Those are the ranges from the EI article. You can dose to target the upper values given above from Day 0 and then start your normal EI dosing. However, in practice you will likely end up around there in 2-3 weeks time in any case with 50% weekly water changes.

Optimal, need, minimum are difficult targets to figure out and change with the objective, plant species and environmental conditions (light, temperature). If someone says they figured out a single value for the entire diversity of plant species, goals and conditions it's worth closing the that page or book.

I would also refer to the image from the original article :

To maximize the growth rate you will need to be at the top of the curve. As you increase the NO3 availability plants tend to get larger leaves and bigger stems. For some plants this is maximized in the hundreds of mg/L NO3 range. Other plants will not show great improvement above 10 mg/L NO3. For many it's not worth keeping hundreds of mg/L NO3 in their tank with fish and shrimp just to get extra large leaves. For a plant farm or a giant Hygrophila competition it might be worth it ... different objectives. Thus the 10-30 mg/L range seems to be a good point for many plants to achieve good growth rates in line with most aquarists' objectives.

Minimum/"enough" values are also tricky to figure out because visible deficiencies often become apparent after weeks of lacking those nutrients. With NO3 deficiency the first visible response is smaller growth then with some plants reddening of the new leaves (eg. Rotala spp.). Plants are great, they can make use of stored reserves, older tissue and adapt their uptake mechanisms to very low values. These coping mechanisms allow the plant to survive until the nutrient concentrations reach the ranges suggested above. The dosing suggested for EI is easily in excess of many setups* and will get you in those suggested ranges with a few weeks.

Hope this clarified some issues, let me know if you have other questions.

*aquariums with fresh aquasoil will uptake more phosphate at the start. Aquariums with heavy anoxic conditions will remove more NO3.


New Member
Oct 6, 2021
Hi Allwissend,
Thank you for your explanation. I indeed noticed that my anubias and vallisneria only grow well at higher NO3 values (30+ppm). Also the stems of the nymphea seem to be thicker then.
I'm still struggeling with discoloration of leave edges (they look green when new bus soon they get brown edges, mainly on anubiases polysperma and hydrocytiles). I was told it was caused by shortage of macro's but I thought I was already on the high side. Maybe these plants types need even higer NO3 values??


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