Excess Algae in NFT Channel for Lettuce

by Stephen
(Arlington, VA)

Manually cleaning the NFT channels of algae has become a problem. Is there an algaecide labeled for food crops that can be added to the nutrient solution? If not, any recommendations for cleaning algae between crops in a greenhouse environment?

Answer: Stephen- I personally have never considered using algaecide or fungicide on any of my consumable crops....at least not anything poisonous to humans. Especially with lettuce, being such a soft-tissue crop, I would be worried about the poisons making their way into the plant tissue. In my opinion, the best solution for algae growth is prevention.

Algae requires the presence of three things in order to grow and flourish. They are: water, nutrients, and light. Obviously, you have nutrient solution flowing through your entire hydroponic gardening system. Therefore, in order to prevent the growth (or at least minimize the growth) of algae in your system, you need to take the light out of the equation. This means, wherever possible, you need to prevent light from coming in contact with your nutrient solution.

To do this, make sure you are using a light-proof nutrient reservoir with a light-proof lid. Your NFT channels should be draped or covered in thick, black plastic sheeting except for each plant site. Where the nutrient solution enters the hydroponic system (and where it exits the system and returns to the nutrient reservoir), the nutrient solution should not be openly exposed to any light. The more light you can exclude from the nutrient solution, the less of a problem you will have with algae.

Finally, you can use Hydrogen Peroxide in small amounts to help prevent algae growth in the system as it operates. Be sure to follow the link above and read everything carefully, as there are a few important things to consider when using Hydrogen Peroxide around living plants and edible crops. Hope this helps you out Stephen, and Happy Growing!