Macronutrients: Nitrogen, Phosphorus, Potassium

Dosing macronutrients can sometimes be a headache, but it can also be fun and useful. It's a headache because most of us don't have the equipment to test for some of the essential elements needed for lush aquatic plants. However, you can try to determine on your dosing without using reading equipment from looking at the symptoms your aquarium and plants are exhibiting. This task can be daunting, especially when you don't have much experience in diagnosing nutrient deficits or excess. It get's even more complicated, when you consider that an excess or deficit in one nutrient can inhibit the uptake of the nutrient that is plentiful in the water column. 

In the macronutrients series, I'll outline the basics in diagnosing nutrient levels in your aquarium through monitoring plant visual symptoms. Let's begin with Nitrogen, and it's interaction with phosphorus and potassium, as they are the main nutrients and those that we do have equipment to test with to verify out predictions. You can have a very successful tank just by fine tuning these three nutrients. 

The essential mineral elements, also known as macronutrients,  includes the following: Nitrogen, Phosphorus, Potassium (NPK), calcium, sulfur, and magnesium.

Aquatic plants prefer the uptake of ammonium over nitrates. Ammonium is not toxic, compared to it's counter parts, ammonia and nitrites. Ammonium is best up taken from the leaf structures of the plant. Ammonium (Nitrogen) interacts with phosphorus at a ratio of 10:1. The excess of phosphorus is often found in relation to algae blooms, and can cause problems when too high. Likewise, low phosphates can cause a high nitrate tank to appear problem free, thus only masking the problem. Nitrogen also interacts with Potassium at a 1:1 ratio. It is because of this relationship that aquarium fertilizers almost never includes phosphorus but includes potassium. Phosphorus can be found in the food we feed our pets, as they're necessary nutrients to a strong exoskeleton. But since not all of the nutrients is absorbed, their byproduct releases phosphorus into the water column. The uptake of nitrogen stimulates the uptake of the cations.

It's important to remember that chemicals such as Chloride and hydroxyl anion restricts the uptake of nitrates causing the entire plant to turn yellow green. The symptoms are equivalent to insufficient nitrogen in the aquarium (ammonia/ammonium, nitrites and nitrates). The leaves will turn from light green to yellow, with older leaves affected more yellow than younger. Deficiency symptoms show first in old leaves. Recovery is also immediate and fast, however older leaves usually do not recover from the deficiency.

Excess nitrates will cause dark green weak leaves, but with succulent foliage. Plants prefer to uptake phosphorus through the roots. Micronutrients work in relations to phosphorus. I'll get more into this in a later post, but keep in mind that it is important to keep Phosphorus to zinc at a rate of 200:1. Similarly to the other micronutrients, include Mn, Fe, Cu, and Zn.

Optimum levels:

Nitrogen should be at 10-40ppm 

Phosphorus 1-3 ppm

Potassium should be 10-40ppm