Quick verdict
A 9 by 14 inch nylon mesh bag with 400 micron openings and bound seams, made in the USA, that holds compost or worm castings in a 5 gallon bucket brewer so the microbes and soluble nutrients wash into the water while the solids stay in the bag. Four hundred microns is the size that lets fungi and bacteria through and keeps grit out of the sprayer. It is the one consumable a tea brewer needs and this one lasts for years of brews.
Strengths
- Four hundred micron mesh passes microbes and holds solids
- Bound seams and strong nylon survive years of brewing
- Sized for a 5 gallon bucket
- Made in the USA
- Rinses clean and dries fast
Weaknesses
- Only a bag; brewer, pump and castings are separate
- Nine by 14 inches holds a few cups of castings, not a bucketful
- Nylon stains with use, which is cosmetic
The overall YardToolLab Score is out of 100. Section scores are out of 10.
The Part of the Brewer That Matters Most
A compost tea brewer is a bucket, an air pump and a bag of castings in the water, and the bag decides what gets into the tea. Too fine and the fungi stay in the bag; too coarse and the sprayer clogs with grit. TeaLAB’s bag is 400 micron nylon with bound seams, 9 by 14 inches for a 5 gallon bucket, made in the USA to be used for years.
This review is based on the maker’s specifications and on how mesh bags perform in aerated compost tea brewing generally. We have not used this bag ourselves.
Mesh Size
Four hundred microns is the figure compost tea makers settled on. Bacteria, fungal hyphae and protozoa pass through into the water, where aeration multiplies them; compost particles stay in the bag so the finished tea goes through a sprayer without blocking it. A paint strainer bag is close in mesh and far weaker.
Brewing
Put two or three cups of worm castings or finished compost in the bag, tie it and hang it in the bucket so it sits in the bubbles from the aerator. Brew 24 to 36 hours with a little molasses in the water. Lift the bag, squeeze gently and use the tea the same day. The spent castings go on the garden.
Durability
Nylon does not rot in a wet bucket and the bound seams do not fray with squeezing. Rinse it under the tap after each brew, let it dry and it is ready for the next. Stains are cosmetic and inevitable.
What It Is Not
It is a bag. The aerator, the bucket and the castings are separate, and the Bag-A-Nut Worm Brew aerator or a large aquarium pump with stones does the bubbling.
Who Should Buy It
- Anyone brewing compost or worm tea in a bucket.
- Worm bin owners with castings to use.
- Gardeners whose paint strainer bags keep tearing.
Common Owner Complaints
Wanting a bigger bag for more castings. Two or three cups is the right dose for 5 gallons.
Technique Tips
Tie the bag with a loop of cord that hooks over the bucket rim so the bag hangs in the moving water rather than sitting on the bottom where it blocks the aerator. Massage the bag gently a couple of times during the brew to release more biology. Rinse it inside out under the tap the moment the brew ends; dried castings are hard to shift from the mesh.
Storage
Dry it fully before folding it into the brewing bucket with the aerator. A damp bag stored in a closed bucket grows the wrong things.
Alternatives to Consider
A 5 gallon paint strainer bag for a cheap, short-lived version. Larger TeaLAB bags for 20 gallon brewers. A rigid mesh basket brewer that needs no bag.
Verdict
The right mesh at the right size, made to last: this bag is the small part of a tea brewer worth getting right. Load it lightly, hang it in the bubbles and rinse it after every brew.
Full specifications
TeaLAB 400 Micron Nylon Mesh Compost Tea Brew Bag, 5 Gallon Bucket Size, 9 x 14 Inches, Made in USA FAQs
Fine enough to keep compost particles out of the brew and the sprayer, open enough for bacteria, fungal strands and protozoa to pass into the water. Finer bags filter out the biology; coarser ones let grit through.
Fill with two or three cups of castings or compost, tie the top, hang it in the bucket with the aerator running and brew 24 to 36 hours. Lift it out, squeeze gently and the tea is ready.
Years. Rinse it after each brew and dry it; the nylon does not rot and the bound seams do not fray.
Paint strainers are a similar mesh and cheaper, and they tear within a few brews. This is the durable version.
