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Homemade Compost Tea

Compost tea is a nutrient-rich liquid fertilizer made by steeping finished compost in dechlorinated water with aeration, optionally boosted with molasses, fish emulsion, and kelp powder. It activates beneficial microbes that improve plant health and soil vitality.
Print Recipe Pin Recipe
Prep Time 15 minutes
Cook Time 2 days
Total Time 2 days 15 minutes
Servings: 5 gallons
Ingredients Equipment Method Notes

Ingredients
  

Base Recipe
  • 1 to 2 cups finished compost not fresh or hot compost
  • 5 gallons dechlorinated water chlorine kills beneficial microbes
  • Air pump with airstone for continuous aeration
Optional Microbial Boosters
  • 1 to 2 tablespoons unsulfured molasses feeds microbes
  • 1 to 2 tablespoons fish emulsion nutrient boost
  • 1 tablespoon kelp powder trace minerals
  • Aerated compost tea starter culture optional commercial option

Equipment

  • Large bucket or food-grade container (5 gallons minimum)
  • Mesh bag or old pillowcase for holding compost
  • Air pump with airstone (aquarium pump)
  • Measuring cup or kitchen scale
  • Stirring stick or paddle
  • Strainer or cheesecloth for filtering
  • Spray bottle or watering can for application
  • Thermometer to check water temperature

Method
 

  1. Fill your 5-gallon bucket with dechlorinated water and let it sit at room temperature for at least 24 hours if using tap water to allow chlorine to evaporate.
  2. Place 1 to 2 cups of finished compost into a mesh bag or old pillowcase and tie it closed.
  3. Submerge the tied compost bag fully into the bucket of water.
  4. Add optional 1 to 2 tablespoons unsulfured molasses, 1 to 2 tablespoons fish emulsion, and 1 tablespoon kelp powder; stir gently to dissolve and distribute.
  5. Place the airstone from your aquarium pump into the bottom of the bucket and turn on the pump to begin continuous aeration.
  6. Keep the bucket in a shaded location at 65 to 75°F (18 to 24°C) and brew the compost tea for 24 to 48 hours depending on water temperature.
  7. Check the tea smell; it should smell earthy and rich, not sour or rotten. If it smells vinegary or like sulfur, discard and start over.
  8. Turn off the air pump and strain the tea through cheesecloth or a fine strainer into containers, leaving compost solids behind.
  9. Use the strained compost tea immediately within 4 hours for maximum microbial viability.
  10. Remove the mesh bag and compost solids and return them to your compost pile.

Notes

Never let finished compost tea sit unused for more than 4 hours; beneficial microbes die quickly once aeration stops. Use fresh batches regularly for best results.