All the ingredients you need to brew up to 250L of actively aerated compost tea (AACT), formulated to feed soil biology and support healthy, vigorous plant growth. This curated ingredient kit promotes a diverse community of beneficial microbes and helps unlock nutrients in living soil systems. Suitable for both veg and bloom stages, and excellent for houseplants, vegetable starts, flowers, raised beds, and gardens of all kinds.
Compost tea is one of the simplest ways to bring your soil to life. A well-brewed tea delivers a burst of living microbes that invigorate the root zone and help your plants access the nutrients already in your soil. With regular weekly use, growers report stronger root systems, healthier foliage, and more vigorous growth over time.
What's Included:
- 1 x 16L Optimize Organics Compost & Castings Blend
- 1 x 1kg Microbe Multiplier
- 1 x 500ml Wild Fish Hydrolysate
- 1 x 500ml Unsulphured Blackstrap Molasses
Why Use This Kit
- Provides the essential ingredients for brewing microbe-rich compost tea
- Designed to support both bacterial and fungal populations for balanced biology
- Helps improve nutrient cycling, root development, and plant vitality
- Gentle enough to apply weekly throughout the entire growing season
How to Brew Your Compost Tea
Use the brewing chart below to measure the right amount of each ingredient for your water volume, whether you're brewing in a 5 gallon pail, a barrel, or a tote. The "per litre" row lets you scale to any custom batch size.
Step 1: Fill Your Container
Fill your brewing vessel with clean water and let it come up to room temperature, not too cold or hot. If your water is cold, give it around 24 hours to warm up first, setting it in a greenhouse or out on a warm day works well, since a cold brew develops much more slowly and your microbes won't multiply the way you want. If you're in a rush, you can stir in some boiling water to bring it up to temperature faster.
Whenever possible, use filtered water, rainwater, or well water rather than chlorinated city water, since the chlorine and chloramine in municipal supplies are added to kill bacteria, which is exactly the opposite of what you want in a compost tea.
If you must use city water, the simplest fix is a filter. Our GrowRite Garden Hose Filter removes both chlorine and chloramine right as you fill.
If you don't have a filter, here's a tip from soil biologist Dr. Elaine Ingham, who pioneered modern actively aerated compost tea: dechlorinate with humic acid. The large humic molecules complex the chlorine and chloramine, binding them so they can no longer harm your soil biology, and the dosing isn't critical. Just add liquid or powdered humic acid to your water and stir until it takes on a slight, tea-colored tint. Once the color changes, you have enough. As a bonus, humic acid is also an excellent food source for beneficial fungi, so it does double duty in your brew.
Step 2: Add the Fish Hydrolysate
Stir your measured Wild Fish Hydrolysate directly into the water.
Step 3: Dissolve the Molasses
In a small container, mix your measured Unsulphured Blackstrap Molasses into a little warm water until fully dissolved, then pour it into the brew. Dissolving it first prevents clumping and helps it disperse evenly.
Step 4: Add Compost & Castings and Microbe Multiplier to the Brew Bag
Place your measured Compost & Castings Blend and Microbe Multiplier into your mesh brew bag. Zip it shut, submerge it, and gently massage the bag so water moves evenly through the contents, helping the microbes disperse and activate. Massage the bag a few times during the brew cycle to prevent the material from compacting and to keep fresh water flowing through for a strong extraction. For barrel or tote brews, split the compost across a few brew bags so no bag is more than half full, which lets water flow through freely for better extraction.
Step 5: Actively Aerate for 24 to 36 Hours
Add air stones connected to an air pump sized for your brew volume, and keep it running constantly.
If you don't already have a brewing setup, our Compost Tea Equipment Kit which is for a 5 gallon pail sized brew, includes a properly sized pump, air stones, a brew bag, and tubing ready to go. Strong aeration is the most important part of a good brew, so make sure the entire surface is in active, rolling motion. In cooler rooms, allow up to 48 hours to fully develop the microbial population.
Step 6: Apply as Soon as the Brew Is Ready
Compost tea is alive, and the microbes start to decline once aeration stops. Apply it as soon as the brew is ready, and do not let it sit with the pump off. Use it as a soil drench, or strain well for a foliar spray.
Optional: Check Your Brew Under a Microscope 🦠🔬
If you really want to be on top of things, it's pretty cool to observe the microbes yourself under a simple microscope. Watching the bacteria, fungi, protozoa, and nematodes come to life lets you hone in on the perfect timing and apply your tea right at peak biology. That said, it's completely optional. We've done years of R&D to dial in the brew times in the chart above, so as long as you follow the instructions, you'll still achieve great results without one.
