How to brew a microbial tea that actually works.

Aerated compost tea is one of the most effective things you can do for a living soil system and one of the easiest to do badly. The difference between a beneficial brew and a harmful one comes down to oxygen, time, and feedstock quality — and most guides skim over all three.

Here is what actually matters.

Oxygen is everything. Anaerobic brewing — leaving compost to steep without aeration — produces a liquid that can harm the microbial populations you're trying to feed. You need a continuous air pump that keeps dissolved oxygen above 6 ppm throughout the brew cycle. This means a proper aquarium pump rated for your volume, not a diffuser stone in a bucket.

Time is a narrow window. Beneficial populations peak between 24 and 36 hours at 20°C. Beyond 36 hours, the biology shifts — beneficial bacteria tire, and organisms you don't want begin to dominate. Set a timer and apply within 4 hours of finishing the brew. Refrigeration doesn't save it.

Feedstock quality determines everything downstream. The best brewing base is worm castings — not compost, not garden soil, castings. They contain the highest density of plant-beneficial organisms. Add unsulphured molasses as a bacterial food source, seaweed extract for trace minerals, and fish hydrolysate for fungal populations. These four ingredients are the entire recipe.

Apply at soil drench rate, not foliar rate. One litre per 10 litres of medium, once per week during vegetative growth. The results are not dramatic in week one. They accumulate over months and become impossible to ignore by season's end.