You have just bought a new isopod culture, or a couple of millipedes from an expo, or some beetle larvae from an online seller. The temptation is to add them straight into an existing setup or your bioactive terrarium. Do not. Quarantine new invertebrates first, every time, even when they look perfectly healthy.
Why bother
New animals can carry grain mites, nematode parasites, fungal spores, and pest species that are not visible to the naked eye. An isopod culture that looks clean in a deli cup at an expo might have a grain mite population that has not yet exploded. A wild-caught millipede may carry nematode worms that will spread through your substrate to every other animal in the enclosure.
Quarantine is not about assuming the seller has done something wrong. It is about accepting that you cannot see everything, and that the cost of a two to four week wait is far less than the cost of a mite infestation spreading across six enclosures or a parasite wiping out your established millipede colony.
It also gives you time to observe the new animal in a controlled setting. Is it eating? Is it active? Does it look healthy up close, or does it have issues that were not obvious when you bought it? Better to find out in a quarantine tub than after you have mixed it in with everything else.
How to set up quarantine
Keep it simple. The quarantine enclosure should provide the basic needs of the species (appropriate temperature, humidity, substrate, food, hides) but does not need to be elaborate. A small plastic tub with ventilation holes, a thin layer of fresh substrate, a piece of cork bark, and a water source is enough for most species.
Use fresh substrate, not substrate from your existing setups. The whole point is isolation. If you transfer substrate from your main colony to the quarantine tub, you are defeating the purpose.
Place the quarantine enclosure in a different room or at least on a different shelf from your other animals if possible. Cross-contamination happens through substrate particles on your hands, mites walking between nearby tubs, and fungus gnats carrying spores from one enclosure to another. Physical distance helps.
Wash your hands between handling the quarantine enclosure and your established setups. Use separate tools (tweezers, misting bottles) if you can. This sounds excessive until you have dealt with a grain mite outbreak that spread to every tub on the same shelf.
How long to quarantine
Two weeks is the minimum. Four weeks is better. Most issues (grain mites, phorid flies, visible parasites) will become apparent within this window. Fungal infections may take longer to show, but a month of observation catches the majority of problems.
During quarantine, check the animal and the enclosure daily. Look at the substrate surface for mites. Look at the food for mould or mite activity. Watch the animal for signs of illness: lethargy, refusal to eat beyond what is normal for the species, unusual posture, visible external parasites, or discharge.
For isopods, quarantine the whole culture together. For species that are solitary (jumping spiders, mantids), each individual gets its own quarantine container, which they need anyway since they must be housed alone.
What to look for during quarantine
Grain mites
Tiny white specks on food, substrate, or enclosure walls. They move slowly but are visible if you look closely, particularly on dark surfaces. If they appear, remove all food, reduce moisture slightly, improve ventilation, and clean the enclosure. Do not add the animals to your main setups until the mite issue is resolved.
Nematodes
Thin, white, thread-like worms in the substrate or occasionally on the animal. More common in wild-caught stock, particularly millipedes and beetles. If you see nematodes, the animal should not be introduced to your other enclosures. Nematodes spread through substrate and are very difficult to eliminate once established.
Phorid flies and fungus gnats
Small flies appearing in or around the quarantine enclosure. They are not harmful to most invertebrates but are a persistent nuisance, breed rapidly in moist substrate, and will infest every enclosure in the room if given the chance. If you spot them during quarantine, deal with them before the new animals go anywhere else. Yellow sticky traps near the enclosure will catch adults. Letting the substrate surface dry slightly between waterings disrupts the larval cycle.
Fungal issues
White mould on substrate is normal and not a concern. Fuzzy growth directly on the animal (on the exoskeleton, around leg joints, or on the body) is mycosis and is serious. An animal showing signs of fungal infection should not be added to other setups. Treat by improving ventilation and keeping the quarantine enclosure clean. Sometimes the animal recovers. Sometimes it does not.
Special cases
Beetle larvae are worth quarantining in fresh flake soil for a month. Contaminated substrate from the seller may harbour mites or fungal spores that will come with the larva. Move the larva to your own clean substrate, keep it warm, and monitor.
Wild-caught animals (millipedes and beetles are the most common wild-caught invertebrates in the UK hobby) should get a longer quarantine period. Four weeks minimum. Wild-caught stock carries parasites and pathogens at higher rates than captive-bred animals. This is one of several reasons captive-bred is generally preferable, but when wild-caught is the only option, quarantine is not negotiable.
If you buy from a seller you trust and have bought from before without issues, quarantine is still worth doing. Even the best breeders can have a mite bloom in one tub that they did not catch before posting. It takes one time for an unquarantined purchase to cause a problem across your whole collection.
After quarantine
Once the quarantine period is up and you have seen no signs of parasites, mites, illness, or pests, the animals can be introduced to their permanent enclosures. Transfer the animals but not the quarantine substrate. Use fresh substrate in the permanent enclosure if it is a new setup, or add the animals directly to an existing established setup.
Clean the quarantine tub, replace the substrate, and keep it ready for next time. You will use it again. There is always a next time.