UTEX sells Modified COMBO Medium at 1X concentration only. Stock solutions and individual components for this specific medium are currently not available for purchase.

Modified COMBO Medium

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Modified COMBO Medium

This modified medium was derived from Guillard and Lorenzen's (1972) WC medium. This medium is used to support growth of cyanobacteria, cryptophytes, green algae, and diatoms.


For 1 L Total
  1. To approximately 900 mL of dH2O, add each of the components in the order specified while stirring continuously.
  2. Adjust the pH to 7.8
  3. Bring the total volume to 1 L with dH2O.
  4. Add vitamins to flask.
  5. Do not autoclave medium! Filter sterilize only.
  6. Store at refrigerator temperature.

# Component Amount Stock Solution Concentration Final Concentration
1 NaNO3
(Fisher BP360-500)
10 mL/L 85.01 g/L 10 mM
2 CaCl22H2O
(Sigma C-3881)
10 mL/L 36.76 g/L 2.5 mM
3 MgSO47H2O
(Sigma 230391)
10 mL/L 36.97 g/L 1.5 mM
4 NaHCO3
(Fisher S 233)
10 mL/L 12.6 g/L 1.5 mM
5 Na2SiO39H2O
(Sigma 307815)
10 mL/L 28.42 g/L 1 mM
6 K2HPO4
(Sigma P 3786)
1 mL/L 8.71 g/L 0.5 mM
7 H3BO3
(Baker 0084)
10 mL/L 24 g/L 3.9 mM
8 KCl (Fisher P 217) 10 mL/L 7.45 g/L 1 mM
9 Algal Trace Elements Solution 10 mL/L
10 Vitamin B12 1 mL/L
11 Biotin Vitamin Solution 1 mL/L
12 Thiamine Vitamin Solution 1 mL/L

Important Notes To Consider:

  • The quality of water, including natural seawater, is important. The term 'dH2O' generally refers to distilled, deionized, distilled/deionized water, Milli-Q water (Millipore Corp.), etc. Natural seawater and natural freshwater should be obtained from a non-polluted source.
  • When dissolving chemicals, wait for the first component to dissolve before adding the second. Stirring, and sometimes the addition of heat, is often required to dissolve the chemicals efficiently. Preparation of stock solutions for frequently made algal culture media make preparing media convenient but also necessary to avoid errors from weighing very tiny amounts.
  • Attention should be given to the pH of the final medium. In most cases, if pH adjustment is required, this occurs before sterilization. Please note that autoclaving removes carbon dioxide from media lacking carbonate stabilizing buffers. This would make the medium very alkaline soon after removal from the autoclave. In these cases, you should wait approximately 24 hours for gaseous equilibrium before inoculating the medium.