Outdoors, soil is alive. Fungi, bacteria, worms and insects turn dead material into something roots can use, and they've been doing it without any help for a very long time. A pot has none of that. Fresh potting mix is mostly bark and coir, and nothing moves in on its own.

• What it is: black soldier fly frass — the manure and shed skins from farmed insects — blended with Australian biochar.
• What it does: brings living microbes, organic matter and a slow, mild feed into a pot that started out with none.
• What it isn't: a fertiliser. It's a soil amendment. Keep feeding as normal.
• Best used: stirred through fresh mix at repotting, or worked into the top few centimetres of a pot that's been in the same mix a while. Also for garden beds and compost.
• How to use: a little goes a long way — rates below.

Frass carries a living microbial community into the mix, along with the organic matter those microbes feed on. As they break it down they release nutrients the roots can take up — slowly, over weeks, not all at once. The biochar keeps it there: a porous charcoal that holds water and nutrients in the root zone instead of letting them wash through, and gives the microbes somewhere to live. Nitrogen 2.1%, phosphorus 0.8%, potassium 1.1%, plus iron, copper, zinc and manganese in trace amounts. Deliberately mild. It's not here to replace your plant food; it's here to make the mix better at holding and delivering what you give it.

It also carries chitin, from the insect exoskeletons — the reason frass gets talked about beyond its nutrients. We've written that up in what is frass?

One thing to know: it's organic matter, and organic matter in a pot that's kept wet is what fungus gnats are looking for. Let the mix dry back properly between waterings and they don't get a foothold. If you've got them already, here's what to do.

This is the Mix step of the Plant Runner Method: get the roots' environment right before you reach for feed. A by-product, not a product — frass is what's left after insects are farmed on food waste; nothing is grown, mined or manufactured to make it. Australian frass, Australian biochar, blended in Melbourne. 500ml jar or 3L pouch, year round.

Pairs with Aroid Mix and Indoor Potting Mix: stir it through at repotting and the mix starts out with the life it would otherwise take months to acquire.

How much to use

Use year round. Water in after applying. Keep the lid on between uses — it's a living product and does best kept dry and out of the sun.