What is the Isopod Temperature Range

Quick answer: most hobby isopods do best somewhere between about 17 and 28°C, but where they sit in that band depends on the species, and it matters because a British home is cooler than many care sheets assume. Measured across 823 English homes, the average through the heating season is 19.0°C, falling to 18.1°C in December, and about 21.5°C in July and August. UK natives and most Mediterranean Armadillidium are happy at that. Dairy Cows, Powders and the other warmer-leaning species tolerate it but breed better at their ideal temperature, which some additional heat can provide from autumn to spring. Cave-origin Cubaris want warmth through the colder months at least, Dwarf Whites for part of the year, and Ardentiella want no heat mat at all. This guide sets out which species sits where.

What a UK Home Actually Measures

Much temperature advice online was written for somewhere else, so it is worth starting with the measured figures. The Energy Follow-Up Survey logged temperatures in 823 English homes for a full year:

• Whole house, heating season (October to April) - 19.0°C
• December, the coldest month - 18.1°C
• July and August, the warmest - about 21.5°C, and more in a hot year: a later round of the survey found living rooms averaging 24.4°C in July 2018
• Spare rooms, garages and conservatories - well below those figures in winter

Keep those numbers in mind when you read the ranges below. A species whose range starts at 18°C is comfortable in an ordinary heated room all year; one whose range starts at 22°C is short of it in most homes even in summer.

Species-Specific Temperature Ranges

The figures below are the ranges on our own care panels, which show where each species does best rather than the most it will put up with.

Cool-Tolerant Species

UK natives, most of the Mediterranean Armadillidium and Porcellio expansus:

• Armadillidium vulgare and morphs (Magic Potion, Hi Yellow, Mosaic) - 18-24°C
• Armadillidium granulatum - 18-22°C, the cool end of the hobby
• Armadillidium maculatum (Zebra) - 18-26°C
• UK natives - Porcellio scaber morphs 17-26°C, Oniscus asellus 15-25°C
• Porcellio expansus (Giant Spanish Isopod) - 18-26°C

An ordinarily heated UK room suits these year-round. Browse our Armadillidium collection for cool-tolerant species.

Warmer-Leaning Species

Species whose ideal starts above an average British winter room:

• Porcellio laevis morphs (Dairy Cow, Snow White, Giant Orange) - 20-26°C
• Porcellionides pruinosus morphs (Powder Orange, Powder Blue and others) - 20-26°C
• Spanish Porcellio - P. hoffmannseggii 20-26°C and P. magnificus 20-28°C
• Armadillidium klugii (Clown, Skeleton, Nebula) - 22-26°C

These tolerate a cooler room but breed better at their ideal temperature, which some additional heat can provide from autumn to spring. Clowns sit warmest of the group: their range starts above an average home even in summer, so a room keeps them going and gentle warmth speeds up breeding. Browse our Porcellio collection.

Warm Species

Cave-origin and tropical species:

• Cubaris species - Rubber Ducky 22-26°C, Panda King 21-27°C, Pak Chong 24-27°C, Cappuccino 21-26°C
• Trichorhina tomentosa (Dwarf Whites) - 22-28°C

A British home sits below these ranges through the colder months and at best near the bottom of them in summer, so Cubaris want a thermostat-controlled heat mat on the side of the tub through the colder months at least, and Dwarf Whites want gentle heat for part of the year in most homes. Warm does not mean hot, though: a Malaysian limestone cave measured across a whole year held a steady 23-25°C, and nothing suggests hotter is better. Browse our Cubaris collection.

Ardentiella: Cooler Than They Look (20-23°C)

Ardentiella (formerly Merulanella) are routinely filed with the warm tropicals and they do not belong there. They tolerate 19-26°C, do best at about 20-23°C, and struggle past 26°C. Keep them in an ordinary heated room with no heat mat: through the winter an average home sits at the cool edge of their range, and in summer it sits inside their best band. In this country heat is the hazard and cold is not - see our Ardentiella care guide.

When Heating Is Worth It

Species That Need None

UK natives, most Mediterranean Armadillidium and Porcellio expansus live well in a normally heated room all year. Ardentiella need no heat mat either: keep them in a heated room, which sits at the cool edge of their range in winter. For these, a thermometer to confirm conditions is the only equipment you need.

Where Additional Heat Helps

• Cave-origin Cubaris - through the colder months at least, because a British home sits below their range
• Dwarf Whites - gentle heat for part of the year in most homes
• Dairy Cows, Powders and the warmer Spanish Porcellio - not to keep them alive, but to keep them breeding well from autumn to spring
• Clowns - their range starts at 22°C, so gentle warmth speeds up a slow colony
• Unheated rooms in winter - spare rooms, garages and outbuildings drop well below the figures above

What NOT to Use

Several heating approaches recommended in older or reptile-focused guides are inappropriate for isopods:

• Heat mats directly under enclosures - create hot spots, dry the substrate, kill isopods. Reptile husbandry methodology that doesn't translate
• Ceramic heat emitters - designed for reptile basking that isopods don't do
• Heat lamps - unnecessary and harmful (isopods avoid light)
• Direct radiant heating - temperature spikes stress isopods

What Works

• A heat mat on the side of the tub - never underneath, always on a thermostat, so one end runs warmer than the other and the animals can choose
• Heat the room, not each enclosure - a small thermostat-controlled heater for a hobby room or shelf when you keep several tubs
• Place enclosures higher in the room - heat rises naturally
• Insulation behind enclosures - reduce heat loss to cold walls

The equipment itself, from wattage to thermostats, is covered in our isopod heating guide.

Why Temperature Matters: The Biology

Isopods are ectothermic (cold-blooded), meaning their body temperature matches their environment. Temperature affects:

• Metabolic rate - higher temperatures speed metabolism; lower temperatures slow it
• Breeding - broods develop faster with warmth, at least up to the low twenties; in Porcellio scaber a brood takes 59 days at 15°C and 23 days at 22°C
• Growth rates - moulting frequency increases at warmer temperatures
• Activity levels - colder temperatures reduce activity; warmer increase it
• Mortality - extreme temperatures cause stress and death

Steady conditions matter as much as the exact figure: a colony copes better with a stable temperature than with swings between cold nights and warm afternoons.

Humidity Connection

Temperature and humidity work together. Warmer air holds more moisture, so:

• Warmer enclosures may need more frequent misting
• Cooler enclosures retain humidity longer
• Sudden temperature changes affect humidity availability

Target humidity at the damp end of the enclosure:

• Mediterranean species - 60-70%
• Tropical species - 75-85%
• Adaptable species - 65-75%

In every case the opposite end should be genuinely dry. Isopods stop detecting humidity differences once the whole enclosure sits above about 65%, so a box held uniformly in these ranges gives them nothing to choose between - see our humidity guide.

Maintain through misting and substrate moisture, NOT through water dishes (which cause drowning risk).

Temperature Gradients

Isopods do not bask the way reptiles do; they simply move to whichever part of the enclosure suits them. In an unheated tub small differences happen on their own, and the hide nearest a cold wall will run slightly cooler than the centre. When you heat a single tub, a mat on one side gives a warmer end and a cooler end, and that choice is the point: never wrap the whole tub, and never heat from below.

Monitoring Temperature

Practical equipment recommendations:

• Digital thermometer/hygrometer combination - sufficient for most UK keepers
• Place at substrate level - air temperature near the top of the enclosure can differ from substrate temperature
• Check at different times of day - temperatures fluctuate with house heating cycles
• Multiple enclosures - worth a thermometer in each location

Browse our accessories collection for monitoring equipment.

Signs of Temperature Problems

Too Cold

• Reduced activity
• Isopods clustering at warmer areas of enclosure
• Slower or stalled breeding
• Delayed moulting
• Reduced feeding

Too Warm

• Excessive surface activity (escaping heat)
• Isopods clustering in cooler/wetter areas
• Increased mortality, particularly during moulting
• Substrate drying out rapidly
• Stress-related deaths

Rapid Fluctuations

• General colony stress
• Reduced breeding success
• Sporadic deaths
• Inconsistent behaviour

Seasonal Considerations

UK keepers notice seasonal variations:

Winter

• A heated home averages about 19°C: fine for natives and most Armadillidium, the cool edge of the range for Ardentiella (still no heat mat), and below the ideal for Dairy Cows, Powders, Clowns, Cubaris and Dwarf Whites
• Conservatory or unheated room enclosures may drop too low
• Check enclosures in colder spaces during cold snaps

Summer

• A typical home runs at around 21 to 22°C, warmer in a hot year
• Overheating is the main risk for Ardentiella, natives and the cool-tolerant Armadillidium
• South-facing rooms can exceed 28°C in summer
• Move enclosures away from direct sunlight, turn heat mats down, and consider cooler rooms during heatwaves

Heating-System Changes

Central heating turning on/off can create temperature fluctuations. Worth placing enclosures away from radiators or vents that cycle.

The Honest Summary

For UK isopod keepers:

• Know your room - an English home averages about 19°C through the heating season and 21.5°C in July and August
• Different species, different ranges - natives and most Armadillidium cool, Dairy Cows, Powders and Clowns warmer, Cubaris and Dwarf Whites warm, Ardentiella cooler than their tropical looks suggest
• Heat where the range needs it - additional heat for the warmer-leaning species through the colder months, a side-mounted mat on a thermostat for Cubaris, no mat for Ardentiella
• Stability matters as much as the number - steady is better than constantly adjusted
• Never heat from below - and leave heat lamps and ceramic heat emitters to the reptiles
• Monitor with a simple thermometer - it tells you where your room sits against each range
• Watch for behavioural signs - clustering, activity changes indicate problems

Whichever species you keep, check its range against your own room before you decide whether it needs heat. Browse our isopods collection to match species to your home.