Almost every keeper sooner or later sees mites, mould or tiny flies in a box. Usually it is no reason to panic – just a sign that conditions need adjusting.

Mites

Where they come from: food (especially oats and bran), leaves and substrate, sometimes new animals. They explode in numbers when it is too wet with too little ventilation and food leftovers lie around.

When they are a problem: a few mites in the substrate are normal. Trouble starts when white “moving dust” covers the food, the walls and the cockroaches themselves – it stresses the animals and in large numbers may contribute to nymph deaths.

What to do:

Dry the box out – keep only a small damp corner and improve ventilation.
Remove leftovers; give dry food in amounts that disappear within a few days.
With a heavy infestation, move the cockroaches to a new clean box with fresh substrate.
You can freeze food and leaves for a few days before use.

Note: some species (e.g. Madagascar hissing cockroaches) host commensal mites that do not harm them – a different situation from grain mites on the food.

Mould

Where it comes from: rotting vegetables and fruit, overly wet substrate and stale air.

What to do: remove mouldy leftovers, serve vegetables on a dish, mist less and improve ventilation. Single patches of mould can be scooped out with a spoon. A clean-up crew helps too – e.g. woodlice or springtails, which eat leftovers and mould.

Flies (fungus gnats, fruit flies)

They appear with excess moisture and rotting fruit. Cut down on fruit, let the top layer of substrate dry and make sure the mesh on the vents is fine enough to keep flies in and out. Yellow sticky traps next to the box catch the adults.

The general rule

Most problems share one cause: too wet and too stuffy. A damp corner instead of a wet box, good ventilation and removing leftovers solve the vast majority of cases.