Another important aspect of the planted aquarium is nutrients.
Plants require macronutrients NPK (nitrogen in the form of nitrates; phosphorus in the form of phosphates; and potassium) amongst other elements. Micronutrients (such as iron, copper, manganese, boron, molybdenum, etc) are also required by plants. It is a common misconception that the addition of phosphates leads to algae; this is not
true. Phosphates are an important part of plant nutrition and is required by plants to grow successfully. As long as there is a balance
between nutrient levels, lighting and carbon dioxide, you can have a successful planted aquarium.
There are several ways to provide these nutrients to plants. In a mixed aquarium (i.e. with fish and plants) with few plants, the wastes from fish can sometimes meet the demands of the plants. However, in heavily planted tanks, the demands of the plants can rarely be met by fish wastes alone. As such, supplementation must occur.
Supplementation can be provided via commercially available products (i.e. Seachem makes such a line of products). Alternatively, one can go for the "chemical" approach. Using this approach, various chemicals can be added to the tank in order to provide the nutrients that plants require. For example:
Potassium nitrate (KNO3) provides potassium and nitrates
Potassium dihydrogen phosphate (KH2PO4) provides potassium and phosphates
Potassium sulfate (K2SO4) provides potassium and sulfur (in the form of sulfates)
Magnesium sulfate (MgSO4) provides magnesium and sulfur (in the form of sulfates)
Trace mix provides various trace elements (Iron, Copper, Molybdenum, etc) that are required
In general, the levels that are desired in a planted aquaria are as follows:
Nitrates: ~10 ppm
Phosphates :~ 1-2 ppm
Potassium: ~20 ppm
Iron: ~1 ppm
There are several different regimes that are available today that can be followed in order to dose appropriately. As I did not write these articles, I will simply link to them here.
The estimative index (EI) method of dosing was created by Tom Barr and can be found here:
The PPS-Pro system was developed by Edward and can be found here: