Leaf Litter (1 litre)

If you strip a woodland setup back to the one thing your animals cannot do without, it is the leaf litter. For isopods, springtails, millipedes and roaches, a layer of fallen, decaying leaves is not decoration sitting on top of the substrate. It is the primary food, the cover they shelter under, and the surface where most of the microfauna in a bioactive tub actually live. This is a bag of that forest floor, aged and ready to lay straight into an enclosure.

The mix is broadleaf and nothing else: birch (Betula), maple (Acer) and oak (Quercus), gathered from clean UK woodland well away from paths and roads. I let it age naturally over several months of dry storage rather than freezing or heat-treating it. That slow drying does two useful things. It sees off any hitchhiking mites or insects present at collection, since almost nothing survives months in a dry sack, and it begins the microbial conditioning that makes the leaves more palatable. I sort and prepare it; the woodland does the hard part.

Offering more than one leaf is better than leaning on a single type. Oak is the one most keepers treat as the staple, tough enough to hold up for weeks in a damp tub and breaking down at a steady pace, so it keeps feeding a colony long after softer leaves have gone. Maple and birch are thinner, so they soften and are eaten sooner, which suits smaller or younger animals and gets fresh food into the enclosure quickly. Between them you get both a fast course and a slow one, and the animals graze whichever they fancy.

Use it as the top layer. Scatter it across the whole surface until you cannot see bare substrate underneath, ideally a few centimetres deep, and top it up as it is grazed down. With isopods there is no real such thing as too much. Porcellio, Armadillidium, Cubaris and Oniscus are all continuous grazers, working through leaves day and night, and a deep litter layer is where they moult, hide and breed. A tub that runs thin on litter tends to go quiet, with less activity and slower breeding. You can also crush a handful and mix it through the substrate for burrowing species, feeding them from below as it rots.

Springtails (Collembola) work the same litter from another angle, feeding on the leaves and on the fungi and mould growing over them, while the damp layer holds the humidity they need. Millipedes lean on decaying leaves just as heavily, and they do best when the litter is paired with something woodier. A scatter of shredded rotten wood alongside the leaves covers both halves of their natural diet. Many forest roaches take it as food and cover too.

The leaves go in dry or lightly misted; inside a humid enclosure they draw in moisture on their own within a day or so, so there is no need to soak them first. Anything left over keeps more or less indefinitely somewhere cool and dry. Just avoid sealing it away while damp, or it will turn mouldy in the bag. And stick to broadleaf. Conifer needles such as pine and spruce carry aromatic oils and resins that most detritivores will not touch, and are best kept out of an invert enclosure altogether.

Common questions

How much should I use? Enough to cover the substrate completely, ideally a few centimetres deep, then topped up before the layer gets thin.

Do I need to freeze or bake it first? No. It has already been through several months of dry storage, so it can go straight into the enclosure, dry or lightly misted.

Can I use it as the whole substrate? It works best as the top layer over a proper substrate rather than as the entire base. For millipedes especially, pair it with rotten wood for a fuller diet.

Whatever you decide to keep on it, a deep and varied leaf layer is the closest thing there is to a single food that quietly does most of the work for you. If you are still choosing your animals, the isopods collection is a sensible place to start.