With the 2HR Aquarist APT-EI, the famous nutrient dosing approach pioneered by Tom Barr is now available in a ready-to-use concentrate that removes the guesswork from trying to recreate this powerful and sometimes elusive formula.
Each week with large (50%) water changes. The aim is to provide plants with non-limiting amounts of nutrients.
The EI philosophy in simplified form is as follows: Fundamentally, it is difficult to gauge with precision the exact uptake rates in a tank for any particular nutrient. This is especially so when the tank has different types of plants and other growth parameters involved (light/CO2). However, dosing everything "in excess" removes any possible nutrient deficiency from the analysis (we assume plants are getting all the nutrients they require through the plentiful amount in the water column) and allows the aquarist to focus on tweaking the other growth variables: light, CO2 levels (this is usually the hardest thing to get right), and other water parameters.
But what about algae? EI theory is based on the idea that if plant growth is taken cared of, plant mass will out-compete algae. It says that algae presence is not determined by whether nutrients are available or not, but rather whether or not there is sufficient plant mass to compete algae (not only in terms of nutrients, but space, light). Healthy plants are the best defence against algae. This is covered more in the portion about diagnosing algae issues.
A weekly cumulative dose of nutrients according to EI would be around:
NO3 - up to 20 - 30ppm
PO4 - up to 5 - 7ppm
K - up to 20 - 30ppm
Fe/traces - up to 0.5 - 1ppm
Dose 5ml per 100L 3 times per week or 2ml per 100L daily.