Mineral nutrients are fussy

Camellia Japonica

When we think of plant nutrients, we usually think of mineral nutrients- these are what are commonly supplemented by growers in the form of a fertilizer, manure, compost, or other organic nutrient addition. Many of them are also available or unavailable in the soil, depending on where you live and what kind of soil you have.

By and large, mineral nutrients can be a bit fussy, and just because they’re present in your system doesn’t mean they’re available. Lots of different things influence whether mineral nutrients are available, but the most important thing is pH. Some minerals are only available at higher pH values, but more are only available at low pH values. This can make the lives of aquaponic growers pretty difficult at times.

When a nutrient is present in your system, but not available, usually that mineral is what we called “precipitated out of solution.”

Basically this means that instead of being dissolved in the water in the system, the nutrient becomes a solid and usually settles on the bottom of the tank, or attaches to a piece of gravel, or other surface in your system. This means that while the nutrient is technically there, it’s not available for the plant to take up. The best example of this is iron.

Iron is often present in aquaponic systems, however, because of system pH and dissolved oxygen, it typically isn’t very available to the plants. Instead, it often exists as a solid precipitate in the system. Mineral plant nutrients are divided into three groups- primary plant nutrients, secondary plant nutrients, and micro-nutrients.

http://blog.brightagrotech.com/plant-nutrients-in-aquaponic-systems/

Grace Albritton Camellia Japonica