To prepare a nutrient medium for *Spirulina*, the concentrations vary significantly depending on whether you are following a rigorous laboratory protocol (like Zarrouk's) or a simplified method for small-scale production.
Below are the quantities required for 1 Liter of water
1. Zarrouk’s Medium (Laboratory Standard)
This is the scientific gold standard for optimized growth. It provides a balanced suite of macro- and micronutrients.
| Component | Amount (per Liter) |
| **Sodium Bicarbonate (NaHCO_3)** | 16.80 g |
| **Sodium Nitrate (NaNO_3)** | 2.50 g |
| **Dipotassium Phosphate (K_2HPO_4)** | 0.50 g |
| **Potassium Sulfate (K_2SO_4)** | 1.00 g |
| **Sodium Chloride (NaCl)** | 1.00 g |
| **Magnesium Sulfate (MgSO_4 \cdot 7H_2O)** | 0.20 g |
| **Calcium Chloride (CaCl_2 \cdot 2H_2O)** | 0.04 g |
| **Iron Sulfate (FeSO_4 \cdot 7H_2O)** | 0.01 g |
*Note: In professional settings, trace elements (boron, manganese, zinc, copper, molybdenum) are added in minute quantities using a concentrated stock solution.
2. Simplified Protocol (Small-Scale/Domestic)
If you are managing a smaller unit and want to avoid complex lab-grade trace elements, this "simplified" recipe is often cited for reliable home or small-batch cultivation.
| Component | Amount (per Liter) |
| **Sodium Bicarbonate** | 16.0 g |
| **Sodium Nitrate** | 2.0 g |
| **Dipotassium Phosphate** | 0.5 g |
| **Potassium Sulfate** | 1.0 g |
| **Sodium Chloride** | 2.0 g |
| **Iron Sulfate** | 0.1 g (100 mg) |
Critical Preparation Tips
Dissolution Strategy: Always dissolve your **Sodium Bicarbonate** first. It acts as the primary buffer. If you try to dissolve the other minerals in acidic water, the pH may fluctuate unexpectedly.
The Iron Factor: Iron is often the limiting factor for growth. It must be in a bioavailable form. If you are not using EDTA (a chelating agent), ensure your iron source is very finely ground and thoroughly mixed, or it may precipitate out of the solution at the high pH required for *Spirulina*.
Water Source: As mentioned previously, ensure your water is strictly free of chlorine. Using deionized water is preferred if you are preparing your own concentrated stocks to ensure you are not adding unknown minerals from tap or well water that could interfere with the delicate mineral balance. You can also use RO water which is pre sterilized with UV filter.