Why Did My Isopod Colony Crash?

There is nothing more confusing and disheartening than seeing a once-thriving isopod colony suddenly dwindle in numbers, or worse, show no signs of life. The word used in the hobby for this curious event is "crashing". The exact reasons behind a crash may never be truly known, but there are a range of early warning signs to look out for, and a diagnostic approach that helps either prevent a future crash or at the very least provide some closure and lessons for the future.

This is our comprehensive troubleshooting guide. For a shorter overview see our companion article why isopod colonies crash.

Diagnostic First Steps

Before diving into the long list of potential causes, run through these initial checks:

How long has the decline been happening? Sudden mass die-off vs gradual decline have different likely causes
When did you last open the enclosure? Recent disturbance, new substrate, new food can correlate with timing
What's the temperature and humidity? Check actual readings, not assumed values
Has anything changed in your home environment? Pest control treatments, new cleaning products, central heating switching on or off
Are there visible animals at all? Or is the colony completely silent?
Any new arrivals to the colony recently? Wild-caught isopods or specimens from unknown sources?

The pattern of decline often points to the cause. Sudden mass deaths suggest acute issues (chemical exposure, temperature shock, ammonia spike). Gradual decline over weeks suggests chronic issues (nutrition, ventilation, substrate degradation).

The Potential Causes

The following list isn't meant to be exhaustive - there are no doubt other potential factors that may cause a crash. But these are the main considerations:

Illness

Like all other living things, isopods are susceptible to disease and illness which can cause fatalities or full colony crashes. Unfortunately, isopod pathology is under-studied compared to vertebrate veterinary medicine, so specific diagnosis is rarely possible. Prevention through quarantine of new arrivals and careful sourcing is your best defence.

Species Choice

There are believed to be over 10,000 isopod species worldwide, but not all are easy to keep. Some species such as the Laureola sp. "White Skull Spiky" or Isopoda sp. "Thai Spike" have expert-level care needs - unforgiving to non-meticulous keepers. If you're new to the hobby and lost a colony of a demanding species, the issue may be the species mismatch with experience level, not your husbandry per se.

Drying Out

Isopods are more vulnerable to desiccation than many keepers realise. Terrestrial isopods breathe through pleopodal lungs (also called pseudotracheae) - modified leg structures on the underside that depend on humidity to function. Note: terrestrial isopods don't breathe through gills despite being crustaceans - gills are for aquatic isopod relatives. The pleopodal lungs evolved as an adaptation to land life, but they still require moisture to work.

If the enclosure dries out below the species-specific minimum, isopods cannot respire effectively. Cubaris want it damp, mostly 60-85% by species across our listings, with the still-air group, the Panda King family among them, kept high and even; Ardentiella want less than people expect, in the 60s to low 70s; temperate species tolerate 50-70% with humidity microclimates. A gradient only works if one end stays drier than the other, with both ends inside the species' range.

Inter-Individual Competition and Cannibalism

Some species of isopod are very protein-hungry. If there isn't enough protein-rich food available, isopods are known to succumb to cannibalism. Our experience has seen this predatory and aggressive behaviour in Porcellio laevis, Porcellio scaber, and Porcellio ornatus, which can become opportunistic feeders amongst their cohab neighbours, particularly targeting freshly-moulted vulnerable individuals.

For more on this see our aggression article.

Overcrowding

Some species grow larger than others and need ample space. Some breed quicker than others and can quickly overpopulate an enclosure. This can cause the entire ecosystem to go out of balance and crash.

To avoid this:

Consider increasing the size of your enclosure
Split the colony into multiple enclosures
Use excess isopods as feeders or cleanup crew in other enclosures (provided those aren't too arid for them)
Sell some privately, at an invertebrate show, or to your local pet shop

For more see our overpopulation article.

Temperature

Too hot or too cold can be harmful to isopods. For this reason, many isopod breeders only ship isopods depending on the weather. Different species tolerate different temperatures - for most Cubaris in the hobby, the low-to-mid twenties by species; for Ardentiella, 19-26°C, best at about 20-23°C; for most Mediterranean Armadillidium 18-24°C, and for Mediterranean Porcellio mostly 18-26°C (20-26°C for Dairy Cows and the rest of P. laevis and for P. hoffmannseggii, 20-28°C for P. magnificus); for UK natives 17-26°C (Porcellio scaber morphs) or 15-25°C (Oniscus asellus). Research the specific needs of your species.

For more see our temperature article.

Pesticides and Chemicals

Isopods can come into contact with pesticides or chemicals through their food, leaf litter, and substrate. We recommend:

Organic foods where possible
Pesticide-free leaf litter and substrate
Avoiding pest control sprays near enclosures
Caution with new cleaning products in the same room
Avoiding scented candles, plug-in air fresheners, or insecticide-based products near setups

On water: UK tap water is generally safe for isopods in normal misting use. Letting tap water sit overnight reduces chlorine but doesn't address chloramine (which doesn't evaporate). If you want extra caution, use filtered water for sensitive species, but most species tolerate UK tap water fine.

Parasites

Only deal with reputable breeders, and do not mix an existing thriving colony with wild-caught isopods. If collecting your own leaf litter and substrate, be sure to sterilise them by baking, boiling, or freezing - whichever method suits you best.

Common parasite/pest concerns:

Predatory mites - small, fast-moving mites that eat springtails and other tiny animals; we know of no evidence that they harm isopods
Grain mites - feed on leftovers and mould; we know of no evidence they harm isopods, but a bloom means too much food and too little airflow
Nematodes - generally less significant for terrestrial isopods but can establish
Wild-caught contamination - even healthy-looking wild isopods can carry parasites that crash captive colonies

Predators

Depending on the accessibility of your enclosures, predators can easily invade and have their very own personal isopod buffet. We speak from experience - we found one of our colonies' numbers were slowly on the decline. On careful investigation we discovered a house spider had made a home in the enclosure and was living his best life! For more see our predators article.

Other potential predators to consider:

House spiders
Centipedes (occasionally finding their way in)
Other invertebrates that hitch-hiked in with substrate
If keeping isopods with other animals - over-predation by the larger species

Too Much Moisture

Excess moisture can drown terrestrial isopods. While they need humidity for respiration, their pleopodal lungs need air-moisture interface, not water immersion. Soggy or waterlogged substrate is dangerous:

Mancae (baby isopods) drown easily in standing water
Adults can become trapped in saturated substrate
Anaerobic conditions develop in wet compacted substrate
Mould and pathogen growth accelerates

The right balance is moist but not wet. Substrate should hold its shape when squeezed but not drip water.

Improper Ventilation

Ventilation matters, but not for the reason usually given. We printed the standard explanation here ourselves - that a sealed box poisons the animals with their own ammonia - and it does not survive the numbers. Woodlice do release most of their nitrogen as gaseous ammonia through the body wall, but the measured seven-day LD50 for Porcellio scaber is around 89 Pa, roughly 880 parts per million, about three times the level that would be immediately dangerous to you. Ammonia is also among the most water-soluble gases there is, and damp substrate absorbs it on a scale that makes headspace accumulation implausible. Hypoxia fails the same test: impairment in the laboratory needs oxygen down at 7%, against 20.9% in normal air.

Here is the mechanism that does hold up. A woodlouse manages its water balance by choosing where to sit. Gunn showed in 1937 that Porcellio scaber reacts to a six per cent difference in relative humidity when the air is around half saturated, and the response does not switch off in humid air: in Waloff's 1941 tests the same species kept to the damper side even when the whole gradient sat between 75% and 95%. So a working moisture gradient needs a drier end rather than a dry one, and you cannot hold a drier end in a sealed box: moisture equalises within hours. Airflow is not there to let gases escape. It is the only thing that lets a gradient exist at all, and without a gradient the colony loses its ability to regulate the variable that matters most. Dixie and colleagues (2015) found a 20-25% drop in humidity outweighed a 5-6°C temperature rise on growth, aggregation and survival alike.

What sealed, wet enclosures do accumulate:

Mould - real, and the usual visible symptom
Anaerobic conditions in compacted, waterlogged substrate
A collapsed gradient, leaving the animals nowhere drier to move to

For Cubaris, and above all the still-air group such as the Panda King family, the rule is: balance high humidity with gentle, constant airflow through fine mesh, never none. Inadequate ventilation is one of the most common silent killers of Cubaris colonies.

Old Substrate

Over time, substrate may need to be changed out depending on the size of your enclosure and colony. Old substrate can become compact, causing some pods not to be able to burrow out (leaving them to eventually suffocate or starve). Other issues may stem from too much frass (droppings) in the original substrate.

When changing out old substrate, store the old material separately and use a cucumber trap to tease out any isopods that may have hijacked within the old substrate. Process this material slowly to rescue any remaining individuals before composting.

Mould

Isopods graze many moulds without harm, and we know of no documented case of a mould infecting living isopods. One lab study did record more deaths when isopods were confined with black mould, though the cause was never confirmed. Nobody has shown how to tell a harmless mould from a harmful one by eye, so go by what the colony does: if a patch is spreading and your isopods are not eating it, remove it.

Step-by-Step Diagnostic Approach

For active troubleshooting of an ongoing crash:

Stop adding new food - remove any uneaten material, especially protein sources
Check temperature and humidity with actual instruments, not estimates
Inspect substrate carefully - smell test (ammonia? sour? rotten?), texture test (compacted? waterlogged? bone-dry?)
Look for live animals - count adults visible in 5-minute observation, check under hides
Check ventilation - hold a tissue near vents to confirm airflow
Examine for pests or predators - mites, spiders, centipedes
Document what you find - take photos, note conditions
Consider partial intervention - improve ventilation, reduce humidity, refresh substrate surface - rather than complete substrate change
Save surviving animals in a fresh, simple setup if conditions look unsalvageable

Prevention Going Forward

To reduce risk of future crashes:

Quarantine all new arrivals for 2-4 weeks before adding to established colonies
Sterilise foraged materials (leaves, wood, substrate) by freezing or baking
Maintain stable conditions - avoid frequent disturbance
Keep multiple smaller colonies rather than one large colony - insurance against single-point failure
Provide good ventilation - especially critical for tropical setups
Consistent calcium provision via cuttlebone
Established springtail populations - essential cleanup partners. Browse our springtail collection
Watch for early warning signs - declining activity, reduced breeding, unusual behaviour, before mass die-off

When to Cut Losses

Sometimes a colony is beyond saving. Signs you may need to start over:

Multiple animals dying daily despite intervention
Substrate condition unsalvageable (deeply contaminated, severely compacted, ammonia-saturated)
Pest populations established and unmanageable
Underlying environmental issue you can't address (no way to provide the right temperature/humidity)

In these cases, rescue any healthy survivors, set them up in a completely fresh enclosure with new substrate and accessories, and treat it as a fresh start. Don't blame yourself - even experienced keepers lose colonies. Document what happened, adjust husbandry for next time.

Connecting With Other Keepers

If you're troubleshooting a difficult crash, reaching out to other keepers can help. PostPods attends multiple UK invertebrate shows throughout the year where you can chat with breeders. See our tour schedule or contact us directly.

For setup essentials browse our accessories collection. For current isopod stock see our isopods collection. For broader husbandry guidance see our first isopods guide.

We hope you found this article useful. Should you have any queries please do not hesitate to contact us.