All plants require an uninterrupted supply of 14 nutrient elements to grow properly.
These are the Macro-nutrients:
- nitrates (N)
- phosphates (P)
- calcium (Ca)
- chloride (Cl)
- sodium (Na)
- magnesium (Mg)
- potassium (K)
- sulfates (S)
And the micro-nutrients:
- iron (Fe)
- boron (B)
- copper (Cu)
- zinc (Zn)
- molybdenum (Mo)
- manganese (Mn)
The macro-nutrients in the aquarium should come from water changes (tap water normally has all these nutrients in small amounts) and small amounts from the fish. Water changes should be done at least every 2 weeks and about 15% should be drained and replaced. This should supply sufficient macros.
The micro-nutrients are different and are normally in short supply in tap water. The other problem with the micro-nutrients is that they are very unstable in their inorganic form and normally precipitate and become unusable.
The Chelate Breakthrough
The discovery of an organic molecule the chelate which binds to metal-ions tightly allowing them to be dissolved in a water solution with no precipitation so making the nutrient available to the plant. This very important for aquatic plants which normally have a very large appetite for iron and may need as much as 4ppm to allow healthy growth without chlorosis.
Chelate Types
There are six types of chelates important to hydroponic growth but only two that need to be mentioned for aquarium plants both for production and in the aquarium.
EDTA (Ethylene-Diamene-Tetra-Acetic-acid) is the first and most commonly known. This is not ideally suited for aquatic plants because it is unstable at a higher pH than 6.0 and generally aquarium conditions are between pH6.0 and pH8.0. This is also a cheaper chelate and so is unfortunately used to cut costs, so absorption is limited.
DTPA (Dethylene-Triamine-Penta-Acetic-acid) would be a better choice and should be more widely used because it is stable up to a pH of 7.5. This is within the aquariums conditions.
When looking for a fertilizer as a very general rule look for:
- Preferably a liquid
- Low or No macro-nutrients
- High Iron (Fe) in the chelated form
- All the other micro-nutrients also in a chelated form if possible
