updated May 2020
What nutrition is required for the planted tank?
Similar to terrestrial plants, aquatic plants require a supply of nutrients to grow well. This has been well studied in terrestrial science, and the chemical elements necessary for growth can be grouped into two major groups:
|Used in large quantities by plants: Nitrogen, Phosphorous, Potassium, Calcium & Magnesium, Sulfur||Used in very small quantities by plants: Iron, Chlorine, Boron, Manganese, Zinc, Copper and Molybdenum.|
Macro-nutrients, together with carbon makes up ~96% of plant mass. Hence, the term macro-nutrients. A lot of the basic building blocks for plants come from air/water; hydrogen, oxygen. The rest of the elements come from soil (for terrestrial plants that's where nutrients accumulate) and water (aquatic plants can take in nutrients through the water column).
Note that Carbon makes up 45% of dry mass, but 'naturally' dissolved carbon in tap water is usually low. Compared to carbon, other macro nutrients make up only a small percentage of dry mass! Plants use 10 times more carbon by mass than all the other macro-nutrients combined. This is why CO2 injection is such a big impact factor in plant growth outcomes. Read more about plant nutrition here.
If you are looking to support good plant growth, the minimum combination that one should add into a tank on a regular basis is Potassium, Iron & Trace elements. (K, Fe + Traces), as these elements are fundamentally missing or insufficient in most tanks. This is because livestock waste and tap water combined is not sufficient.
A far better, more comprehensive combination would include Nitrogen, Phosphorus, Potassium, Magnesium, Iron & Trace elements (NPK, Mg, Fe + Traces), which is the basis for the Capstone / APT range of fertilisers.
There are two approaches to fertilization: dosing directly into the tank with liquid fertilizers (water column dosing approach) and using substrate based fertilizers (rootzone fertilization). Most plants can take in nutrients through both routes, and there are advantages to having nutrients in both locations. This is explored in more detail in this article.
We highly recommend approaching fertilisation from both angles: root and water. Root tabs such as these from API and Osmocote are easy enough to implement in any tank; a few minutes of work to enrich the substrate is something we should not pass up on.
Above: Some species such as Centrolepis drummondiana (often called "Trithuria blood vomit") and Eriocaulon quinquangulare shown above grow significantly faster and more stable with root fertilization (especially with ammonia rich substrates) in a way that is hard to replicate just water column dosing.
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