Fellow Creatures
Pet match quiz
Bedding and substrate

Is this bedding safe?

Softwood shavings and raw corncob are still on shelves and still recommended by shop staff. This is the mistake that gets made before the animal even arrives.

Every bedding and substrate table

Safe, with a caveat, or never: for each kind we have built a table for, and a general list per category for the rest. These are material judgements rather than brand reviews: there are no product names anywhere on this site, so match the generic description to what the label actually says.

Hamsters

Depth is the whole point. A hamster with 16 in of paper bedding behaves like a different animal to one with 1.2 in.

Safe

Dust-extracted paper bedding, 16 in deep or moreDeep enough to hold a tunnel that does not collapse: TVT and Swiss Animal Protection give 16 in, and never less than 8-10 in. This is the single biggest enrichment change you can make.
safe
Kiln-dried aspenMixes well with paper to give the burrow structure.
safe
Plain chinchilla bathing sand in a heavy dishFor coat condition. Sand, never dust.
safe
Hay and plain toilet paper for nestingSafe nesting material a hamster can shred itself.
safe

With a caveat

HempGood absorbency, but on its own it does not hold a burrow. Mix with paper.
with a caveat

Never

Fluffy cotton-wool nesting materialWraps around limbs and is swallowed. Repeatedly implicated in limb injuries and blockages in hamsters.
never
Pine and cedar shavingsAromatic oils; airway irritation and liver effects.
never
Raw corncobBlockage risk, and it moulds.
never
Scented beddingThe hamster's nose lives in it.
never

Read the hamster care guides →

Rabbits

Rabbits need a clean, dry, non-slip floor plus a separate deep litter tray. The two jobs need two materials.

Safe

Paper-based litter in the tray, topped with hayRabbits eat while they toilet. Hay over paper litter serves both habits.
safe
Fleece or washable mats on the living floorNon-slip, warm, and washable.
safe
Straw for outdoor warmthInsulating, and different from hay: straw is bedding, hay is food. An outdoor rabbit needs both.
safe

With a caveat

Wood pelletsVery absorbent in a tray, uncomfortable underfoot as a floor.
with a caveat

Never

Clumping cat litterSwallowed while grooming and eating, and it clumps internally.
never
Pine and cedar shavingsAromatic oils; airway irritation in a species already prone to respiratory disease.
never
Wire mesh floorsCauses sore hocks. Rabbits have no protective pad on the underside of the foot.
never

Check and clean the rear at least twice a day in warm weather, for every rabbit. A soiled or damp rear is what flystrike needs.

Read the rabbit care guides →

Guinea Pigs (American Guinea Pig, Abyssinian Guinea Pig, Skinny Pig (Hairless Guinea Pig) and Teddy Guinea Pig)

Guinea pigs do not burrow, so the priorities are absorbency, dryness and grip.

Safe

Fleece liners over an absorbent layerPopular and comfortable. It only works with absorbency underneath and a wash every few days.
safe
Dust-extracted paper beddingThe simplest reliable option.
safe
Deep soft hay over an absorbent baseFood, bedding and cover at once. Not for a long-coated breed such as the Silkie: loose hay works into the coat and soils it, so use fleece liners over an absorbent layer and offer hay from a rack.
safe

With a caveat

Kiln-dried aspenSafe, but less absorbent than paper for an animal that produces a lot of urine.
with a caveat

Never

Pine and cedar shavingsAromatic oils; respiratory irritation in a species with fragile lungs.
never
Sawdust and very dusty beddingGuinea pigs are prone to respiratory infection, and dust is a direct contributor.
never
Wire mesh floorsCauses sore hocks and trapped feet.
never

Read the American Guinea Pig guide →Read the Abyssinian Guinea Pig guide →Read the Skinny Pig (Hairless Guinea Pig) guide →Read the Teddy Guinea Pig guide →

Rats

For rats, dust is the whole conversation. Their respiratory tract is the weak point of the species.

Safe

Dust-extracted paper beddingThe default. Look for a stated dust-extraction process.
safe
HempLow dust, highly absorbent.
safe
Fleece hammocks and linersRats will use every soft surface you give them. Wash often.
safe

With a caveat

Cardboard beddingFine, but it needs frequent changing, and an ammonia smell means it is already overdue.
with a caveat
Kiln-dried aspenWidely used and free of the aromatic oils in pine and cedar, but the RSPCA advises against aspen bedding for rats because it can cause breathing problems. Dust-extracted paper or hemp is the safer default.
with a caveat

Never

Pine and cedar shavingsTheir aromatic oils irritate the airway and affect the liver. In a species where chronic respiratory disease is among the most common and most serious illnesses, that makes them the worst possible choice.
never
SawdustDust plus softwood.
never
Scented litterFragrance is an irritant.
never

If you can smell ammonia at the cage, the rats have been breathing it for a while. That is a cleaning-frequency problem, not a bedding problem.

Read the rat care guides →

Mice

Mice dig and nest, and their airways are as sensitive as a rat's: dust-free, unscented bedding deep enough to burrow in, plus soft material to build a nest from.

Safe

Dust-extracted paper beddingThe default. Look for 'dust extracted' on the label rather than 'natural'.
safe
Hemp beddingVery absorbent and low dust.
safe
Plain paper, tissue or hay for nestingMice build elaborate nests from material they shred themselves. Unprinted paper only.
safe

With a caveat

Kiln-dried aspen shavingsLow in the aromatic oils that make pine and cedar a problem, but the RSPCA advises against aspen bedding and wood shavings for mice. Dust-extracted paper or hemp is the safer default.
with a caveat
Cardboard-based beddingFine, but it goes soggy quickly and needs changing more often than paper.
with a caveat

Never

Pine and cedar shavingsTheir aromatic oils irritate the airway and affect the liver: laboratory work found liver enzyme changes in mice after about a day on cedar, and enlarged livers in mice kept on pine for months.
never
SawdustDust plus, usually, softwood. Both problems at once.
never
Scented or coloured beddingThe RSPCA advises against fragrant or coloured material; added fragrance is an airway irritant.
never
Cotton wool and fluffy nesting materialIt wraps around limbs and is swallowed.
never
Clumping cat litterSwallowed during grooming, and it clumps inside the animal.
never

Give them enough depth to dig: the RSPCA asks for at least 0.8 in of bedding and the TVT, Germany's veterinary animal-welfare association, about 4 in.

Read the mice care guides →

Gerbils

Gerbils tunnel. Substrate depth is not enrichment for them, it is the enclosure.

Safe

Deep paper and aspen mix, 16 in or moreA gerbil needs a tunnel that holds its shape: TVT, Swiss Animal Protection and the Swiss veterinary office give 16 in. Mixing paper with aspen and a little hay gives it structure.
safe
Plain chinchilla bathing sandEssential for coat condition.
safe
Hay woven through the substrateBinds the burrow walls.
safe

With a caveat

Coco fibreHolds a burrow well, but keep it dry: gerbils are desert animals.
with a caveat

Never

Pine and cedarAromatic oils that irritate the airway.
never
Shallow bedding in a tall cageA gerbil that cannot dig will bar-chew instead, and that is the standard sign of an inadequate setup.
never
Cotton-wool nesting materialEntanglement and ingestion risk.
never

Read the gerbil care guides →

Chinchillas

Chinchillas must stay dry. Their coat is dense enough that damp against the skin causes fungal problems.

Safe

Kiln-dried aspenAbsorbent and dry.
safe
Dust-extracted paper beddingWorks well; change promptly.
safe
Chinchilla bathing dust or fine chinchilla bathing sand, offered for 10 to 15 minutes at a timeA fine product made for chinchillas, never play or builder's sand or general-purpose dusts. Take it out after 10 to 15 minutes: left in, it becomes a litter tray and irritates the eyes.
safe

With a caveat

Fleece linersFine over absorbency, but a chinchilla on damp fleece is a fungal infection waiting to happen.
with a caveat

Never

Pine and cedarAromatic oils that irritate the airway.
never
Water bathsNever bathe a chinchilla in water. The coat does not dry through.
never

Read the chinchilla care guides →

Ferrets

Ferrets do not tunnel through their bedding the way rodents do. The cage needs a litter tray they will use and soft, washable bedding to sleep in.

Safe

Recycled-paper or paper-pellet litter in the trayLow dust, and harmless if a little is swallowed. Ferrets back into corners to toilet, so put a high-backed tray in the corner they choose.
safe
Washable fleece, towels or old blankets in the sleeping areasFerrets burrow under soft fabric to sleep. Wash weekly: ferret odour lives in the bedding rather than in the animal.
safe
Hammocks and sleep sacksUsed constantly. Check for chewed holes and loose threads at every wash.
safe

Never

Clumping clay cat litterDusty, and it clumps if it is swallowed or packs into the nose.
never
Pine and cedar shavingsAromatic oils that irritate the airway.
never
SawdustDust plus, usually, softwood.
never

Read the ferret care guides →

Sugar Gliders

Gliders live up off the floor, so bedding here is mostly about the cage tray and the pouches they sleep in.

Safe

Dust-extracted paper bedding or plain paper in the cage trayCatches the food and droppings that fall from above. Change it often: a nectar-and-fruit diet makes a sticky mess.
safe
Fleece sleeping pouchesSeveral, so no glider is shut out. Wash weekly and check every seam.
safe

With a caveat

Fleece liners on the cage floorFine if washed often; a sticky diet soils them fast.
with a caveat

Never

Pouches or toys with loose threads or frayed fabricThreads catch toes and tails, and a trapped limb can be lost overnight.
never
Pine and cedar shavingsAromatic oils that irritate the airway.
never

Read the sugar glider care guides →

Silkie Guinea Pig

Guinea pigs do not burrow, so the priorities are absorbency, dryness and grip, and for a long coat like the Silkie's, nothing loose that works its way into the coat.

Safe

Fleece liners over an absorbent layerThe usual choice for a long-coated pig, because there is nothing loose to tangle in the coat. It only works with absorbency underneath and a wash every few days.
safe
Dust-extracted paper beddingAbsorbent and low in dust. It is loose, so it catches in a long coat more than fleece does.
safe

With a caveat

Loose hay as beddingHay is food and must always be there, but a deep layer of it as bedding works into a long coat and soils it. Offer it from a rack instead.
with a caveat
Kiln-dried aspenSafe, but less absorbent than paper, and loose shavings work into a backswept coat within hours.
with a caveat

Never

Pine and cedar shavingsAromatic oils; respiratory irritation in a species with fragile lungs.
never
Sawdust and very dusty beddingGuinea pigs are prone to respiratory infection, and dust is a direct contributor.
never
Wire mesh floorsCauses sore hocks and trapped feet.
never

Spot-clean every day: on a long-coated pig a soiled floor soon becomes a soiled coat, and in warm weather that invites flystrike.

Read the Silkie Guinea Pig guide →

Geckos

Match the substrate to the species' humidity, and never let a small gecko stand on anything it can swallow whole.

Safe

Topsoil and play sand mix for arid geckosPacks firm, holds a burrow, and is what a leopard gecko would actually stand on.
safe
Coco fibre and orchid bark for tropical geckosHolds the humidity a crested or day gecko needs.
safe
Paper towelCorrect for quarantine, for hatchlings, and for any animal whose output you are watching.
safe

With a caveat

Sphagnum mossExcellent in a humid hide, poor as a whole-floor substrate: it stays wet.
with a caveat

Never

Calcium sandSold as digestible, which is exactly why it gets eaten. Implicated in impaction.
never
Crushed walnut shellSharp and indigestible.
never
Loose play sand alone for hatchlingsToo easy to swallow at that size.
never

Ground-dwelling geckos such as leopard and fat-tailed geckos need a humid hide whatever the main substrate is, and most of their stuck sheds trace back to its absence. Arboreal geckos get their shedding humidity from misting the whole enclosure, so stuck shed in them usually means the enclosure is too dry.

Read the gecko care guides →

Snakes (Corn Snake, Ball Python, California Kingsnake, Milk Snake, Children's Python, Common Garter Snake, Carpet Python and Common Boa)

For snakes the substrate has to hold the right humidity for the shed, and let the animal get fully under it.

Safe

Cypress mulchHolds humidity without going sour quickly. A common default for tropical snakes.
safe
Aspen shavingsThe classic for colubrids. Excellent for burrowing; replace any patch that gets wet.
safe
Topsoil and coco fibre mixBioactive-ready and holds a burrow.
safe
Sand-topsoil mixFor arid and sandy-soil burrowers such as hognoses: plain topsoil with some play sand mixed in holds a burrow. Keep it dry.
safe
Paper towel or newspaperQuarantine, feeding response problems, and post-surgery.
safe

With a caveat

Aspen in a high-humidity setupIt moulds. Aspen suits dry-side species; wet species need mulch or soil.
with a caveat

Never

Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding.
never
Pure loose sand for species from humid habitatsIt holds little moisture, which makes shed problems more likely, and it does not hold a burrow. A soil mix with some sand is fine for snakes from sandy, dry habitats such as hognoses and sand and rosy boas.
never

Stuck shed and retained eyecaps are usually a humidity failure during the blue phase, not a substrate failure afterwards.

Read the Corn Snake guide →Read the Ball Python guide →Read the California Kingsnake guide →Read the Milk Snake guide →Read the Children's Python guide →Read the Common Garter Snake guide →Read the Carpet Python guide →Read the Common Boa guide →

Bearded Dragons

For a desert lizard the floor should be dry on top and firm enough to hold a burrow; anything chosen to hold humidity is the wrong material.

Safe

Topsoil and play sand mixPlain topsoil with no fertiliser or perlite, mixed with play sand and, if you like, up to about a fifth clay, packed firm enough to hold a burrow. ReptiFiles suggests roughly half sand, 30% topsoil and 20% clay.
safe
Slate or unpolished stone tileEasy to clean, warms well under the basking lamp, and unpolished stone gives grip.
safe
Paper towel or newspaperFor quarantine and for sick or injured animals, not as a long-term floor.
safe

With a caveat

Loose sand alonePack it, or mix it with soil, so it holds a burrow and is not the only thing under the food.
with a caveat

Never

Wood products (cypress mulch, orchid bark, shavings) and coco fibreThey hold the humidity a desert species should not have, and pieces are swallowed with food.
never
Calcium or vitamin sandSold as digestible, which encourages eating it. Implicated in impaction.
never
Crushed nut shellSharp fragments, frequently implicated in impaction.
never
Reptile carpetSnags claws and holds bacteria in the fibres; on ReptiFiles' do-not-use list for bearded dragons.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Impaction is far more often a temperature problem than a substrate problem: an animal that cannot reach its digestive temperature will not pass what it swallows, whatever it is standing on.

Read the bearded dragon care guides →

Uromastyx

For a desert lizard the floor should be dry on top and firm enough to hold a burrow; anything chosen to hold humidity is the wrong material.

Safe

Topsoil and play sand mixFine sand mixed with plain topsoil (no fertiliser or perlite), packed at least 4 in deep and firm enough to hold a burrow. A uromastyx is a dedicated digger, so depth matters as much as material.
safe
Slate or unpolished stone tileEasy to clean and warms well under the basking lamp, but it gives a digger nothing to dig, so pair it with a deep dig area or burrow box.
safe
Paper towel or newspaperFor quarantine and for sick or injured animals, not as a long-term floor.
safe

With a caveat

Loose sand alonePack it, or mix it with soil, so it holds a burrow and is not the only thing under the food.
with a caveat

Never

Wood products (cypress mulch, orchid bark, shavings) and coco fibreThey hold the humidity a desert species should not have, and pieces are swallowed with food.
never
Calcium or vitamin sandSold as digestible, which encourages eating it. Implicated in impaction.
never
Crushed nut shellSharp fragments, frequently implicated in impaction.
never
Reptile carpetSnags claws and holds bacteria in the fibres, and a digger cannot dig in it.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Impaction is far more often a temperature problem than a substrate problem: an animal that cannot reach its digestive temperature will not pass what it swallows, whatever it is standing on.

Read the uromastyx care guides →

Monitors

An ackie lives underground as much as on top: the substrate is packed, damp-enough soil it can tunnel through, and depth is the point.

Safe

Topsoil and play sand mix, packed 12 in deep or morePlain topsoil and play sand at roughly two to one, with no more than a fifth clay if you add any, moistened until it clumps so the burrows hold. ReptiFiles gives 12 in as the minimum for males, 18 in for females and about 24 in as ideal.
safe

With a caveat

Play sand aloneWorks in a pinch, but it holds burrows less well than a soil mix.
with a caveat
Paper towelQuarantine and the short term only: an ackie that cannot dig cannot rest or regulate its temperature properly.
with a caveat

Never

Coco fibre, bark, wood shavings or mulch as the main substrateThey do not hold a tunnel the way packed, damp soil does.
never
Calcium or vitamin sandSold as digestible, which encourages eating it. Implicated in impaction.
never
Crushed nut shell, gravel or reptile carpetNothing to dig in, and nut shell and gravel are swallowed.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

If the tunnels collapse, the mix is too dry: dampen the lower layers rather than the surface.

Read the monitor care guides →

Turtles

For an aquatic turtle the substrate is the tank floor, and the rule is that nothing on it fits in the turtle's mouth.

Safe

Bare bottomEasiest to keep clean, and it hides no waste.
safe
Smooth river stones or slate larger than the turtle's headRinse them, and stand stacked rock on the glass, not on top of sand, so it cannot shift.
safe

With a caveat

Fine aquarium sand, in a thin rinsed layer siphoned regularlySome keepers like it for bottom-walking musk turtles, but turtles swallow it, vets advise against it, and it can be kicked into the filter.
with a caveat

Never

Gravel or pebbles small enough to swallowTurtles swallow them, and swallowed stones can need surgery to remove.
never
Soil, coco fibre, bark, mulch or leaf litter in the waterThey foul the water and clog the filter.
never
Unguarded glass heatersTurtles crack them. Use a heater guard or an in-line heater.
never

Keep the basking dock fully dry. A gravid female needs a separate soil-and-sand nesting box, or she may retain her eggs.

Read the turtle care guides →

Tortoises (Russian Tortoise, Hermann's Tortoise, Greek Tortoise and Sulcata Tortoise)

Tortoise substrate has to hold a burrow and hold moisture, because dry-brooded tortoises pyramid.

Safe

Topsoil and coco coir mix, deep enough to dig intoHolds humidity at the shell without being wet at the surface.
safe
Topsoil or loam with a low sand fractionDeep enough to dig into, dry on the surface and slightly moist lower down. Keep the sand fraction low enough that it still packs and holds a burrow.
safe

With a caveat

Orchid bark over soilFor humid-species tables such as red-foots. Kept damp, it is too wet underfoot for Mediterranean species and sulcatas.
with a caveat

Never

Pure sandEaten during grazing, and it does not hold a burrow.
never
Wood shavings of any softwoodAromatic oils, and they are eaten.
never
Rabbit pellets as a substrateSold for it. It moulds, and the tortoise eats a diet it was never meant to have.
never

Read the Russian Tortoise guide →Read the Hermann's Tortoise guide →Read the Greek Tortoise guide →Read the Sulcata Tortoise guide →

Rosy Boa

A dry-country burrower: the substrate has to stay dry and be deep and loose enough for the snake to bury itself.

Safe

Sand-topsoil mixTopsoil, play sand and a little clay (ReptiFiles gives 40% topsoil, 40% sand and 20% clay by weight), at least 3-4 in deep and kept dry.
safe
Aspen shavings, kept dryLoose and easy to burrow in. Replace any patch that gets wet, because aspen moulds when damp.
safe
Paper towel or newspaperQuarantine, feeding response problems, and post-surgery.
safe

With a caveat

Cypress mulch and coco fibreThey hold humidity, which is wrong for a dry-substrate burrower and invites respiratory and scale problems.
with a caveat
Damp mossInside a humid hide on the cool side only, never over the floor.
with a caveat

Never

Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding.
never
Calcium or vitamin sandSold as digestible, which encourages eating it. Implicated in impaction.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Keep the enclosure dry. ReptiFiles keeps a humid hide of lightly damp substrate or moss on the cool side all the time, while some keepers offer one only during a shed. Feeding on a tile or in a separate container keeps substrate out of the meal.

Read the Rosy Boa guide →

Kenyan Sand Boa

A dry-country burrower: the substrate has to stay dry and be deep and loose enough for the snake to bury itself.

Safe

Sand-topsoil mixAbout 60% plain topsoil to 40% play sand, at least 3-4.5 in deep so the boa can bury itself fully, and kept dry.
safe
Aspen shavings, kept dryLoose and easy to burrow in. Replace any patch that gets wet, because aspen moulds when damp.
safe
Paper towel or newspaperQuarantine, feeding response problems, and post-surgery.
safe

With a caveat

Cypress mulch and coco fibreThey hold humidity, which is wrong for a dry-substrate burrower and invites respiratory and scale problems.
with a caveat
Damp mossInside a humid hide on the cool side only, never over the floor.
with a caveat

Never

Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding.
never
Calcium or vitamin sandSold as digestible, which encourages eating it. Implicated in impaction.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Keep the enclosure dry. ReptiFiles keeps a humid hide of lightly damp substrate or moss on the cool side all the time, while some keepers offer one only during a shed. Feeding on a tile or in a separate container keeps substrate out of the meal.

Read the Kenyan Sand Boa guide →

Western Hognose Snake

A sandy-soil burrower: the substrate has to be deep and loose enough to dig in, firm enough to hold a burrow, and not chosen to hold humidity.

Safe

Sand-topsoil mixAbout 70% plain, untreated topsoil to 30% play sand (ReptiFiles' mix), at least 3 in deep and 4-5 in for a large adult female.
safe
Aspen shavingsCheap, easy to clean and holds a burrow well, but it does not hold moisture. Replace any patch that gets wet, because aspen moulds when damp.
safe

With a caveat

Paper towel or newspaperReptiFiles lists both among the bad hognose substrates, because a burrower cannot dig in them. Use them for quarantine or mite treatment only, never as the long-term floor.
with a caveat
Cypress mulchChosen to hold humidity for tropical snakes. A hognose is kept at low to moderate humidity and digs in sandy soil, so a soil-sand mix or aspen suits it better.
with a caveat

Never

Coconut fibreReptiFiles lists it among the poor substrates for hognoses.
never
GravelListed by ReptiFiles among the poor choices, and no use to a snake that digs.
never
Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Keep humidity low to moderate and the surface dry, with a humid hide during a shed. Clean, dry substrate is what keeps a burrower free of skin and scale infections.

Read the Western Hognose Snake guide →

Red-footed Tortoise

A red-foot is a forest tortoise: the substrate has to hold 70-80% humidity without the surface turning into mud.

Safe

Topsoil and coco fibre mix, at least 4 in deepMoisture-holding and diggable. ReptiFiles' mix is roughly 40% organic topsoil, 40% coconut fibre and 20% play sand by weight.
safe
Cypress mulch or orchid bark mixed in or over soilHolds humidity and resists compaction; the red-foot guide pairs coco coir with cypress mulch.
safe
Leaf litter on topAt least 1 in, for cover and to keep the humidity in.
safe

With a caveat

Sphagnum mossUseful in a humid hide; it stays wet, so not as the whole floor.
with a caveat

Never

Dry sand or sand-heavy mixesThey cannot hold the humidity a red-foot needs.
never
Wood shavings of any softwoodAromatic oils, and they are eaten.
never
Rabbit pellets as a substrateSold for it. It moulds, and the tortoise eats a diet it was never meant to have.
never

The red-foot guide holds 70-80% humidity with daily misting or a fogger; a deep, moisture-holding substrate is what makes that possible.

Read the Red-footed Tortoise guide →

Other Small Pets

Bedding has three jobs: absorb, stay dust-free, and, for the species that burrow, let the animal dig. Anything aromatic is failing the second one.

This is the general small pets substrate list. It is what the tool answers with for Hedgehogs and Degus: every kind in this category without a table of its own.

Safe

Dust-extracted paper beddingThe default for almost every small mammal. Look for 'dust extracted' on the label rather than 'natural'.
safe
Kiln-dried aspen shavingsThe usual safe wood: a hardwood low in the aromatic oils that make pine and cedar a problem. Kiln-dried matters.
safe
Hemp beddingVery absorbent and low dust. More expensive per gallon but goes further.
safe
Soft meadow hay as a top layerFood and bedding at once for herbivores such as degus. Never the only absorbent layer.
safe
Plain shredded paper or paper stripsUnprinted or soy-ink only. Cheap nesting material; poor as the main absorbent layer.
safe
Fleece liners over an absorbent layerOnly works with an absorbent layer underneath and a wash every few days. Fleece alone holds urine against the skin.
safe

With a caveat

Cardboard-based beddingFine, but it goes soggy quickly and needs changing more often than paper.
with a caveat
Sand bathsCorrect and important for chinchillas, degus and gerbils. Use chinchilla bathing sand or a chinchilla dusting clay, never talc or builder's sand.
with a caveat
Hemp or straw pelletsGood absorbency, but too hard to burrow in. Use under a soft layer, not as the whole substrate.
with a caveat

Never

Pine and cedar shavingsThe aromatic oils that make them smell pleasant are the problem: they damage the liver and kidneys and the cells lining the airway. Laboratory work found liver enzyme changes in mice after roughly a day of cedar exposure, taking well over a week away from it to settle, and enlarged livers in mice kept on pine for months.
never
Raw corncobTwo separate problems. It is swallowed and causes intestinal blockage, and it grows mould readily once damp.
never
Cotton wool and fluffy nesting materialSold as bedding, and it wraps around limbs and is swallowed. Repeatedly implicated in amputations in hamsters.
never
Scented or perfumed bedding of any kindAdded fragrance is an airway irritant in an animal whose nose is centimetres from the bedding all day.
never
Clumping cat litterSwallowed during grooming, and it clumps just as effectively inside the animal.
never
SawdustDust plus, usually, softwood. Both problems at once.
never

Depth matters as much as material for burrowing species. A hamster or a gerbil needs about 16 in of substrate it can actually tunnel through; shallow bedding on a large floor is still an inadequate enclosure.

Browse all Small Pets →

Other Reptiles

Substrate choice follows the animal's natural humidity, not the look of the vivarium. Get that pairing right and most substrate arguments disappear.

This is the general reptiles substrate list. It is what the tool answers with for Skinks, Chameleons, Anoles and Water Dragons: every kind in this category without a table of its own.

Safe

Topsoil and coco fibre mixThe usual bioactive-ready base for lizards from humid habitats. Plain topsoil with no fertiliser, no perlite and no wetting agents; keep the lower layers slightly damp. Coco fibre on its own also holds humidity, but rinse it and do not let it go bone dry, which makes it dusty.
safe
Leaf litter over a soil baseCover, humidity and invertebrate habitat in one. Sterilised, from a known source.
safe
Cypress mulch or orchid barkLong-lasting, holds humidity and resists compaction. Cypress specifically, not general 'wood mulch'.
safe
Topsoil and play sand mix, for species from dry habitatsPacks firm and holds a burrow. Plain topsoil with no fertiliser, no perlite and no wetting agents.
safe
Paper towel or newspaperNot attractive, but correct for quarantine, for a new arrival, and for any animal being monitored for output.
safe

With a caveat

Reptile carpetSnags claws and traps bacteria in the fibres. If used, it needs replacing rather than washing, often.
with a caveat
Sand alone for desert speciesReal desert is packed substrate, not loose play sand. Mix it with soil so it holds a burrow.
with a caveat
Bioactive setupsExcellent when established, but the clean-up crew needs weeks to establish before the animal goes in.
with a caveat

Never

Calcium sand and 'digestible' sandsMarketed as safe to eat, which encourages eating it. Implicated in impaction.
never
Crushed walnut shellSharp fragments, frequently implicated in impaction, with no advantage over soil.
never
Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding. They have hardly been studied in reptiles, so leave them out.
never
Uncovered heat mats and unguarded ceramic emittersNot a substrate, but the most common cause of contact burns. Every heat source needs a thermostat, and every emitter needs a guard.
never

Impaction is far more often a temperature problem than a substrate problem: an animal that cannot reach its digestive temperature will not pass what it swallows, whatever it is standing on.

Browse all Reptiles →

Other Freshwater Fish

Substrate in an aquarium is a filter as much as a floor. Most of the biology lives in and on it.

This is the general freshwater fish substrate list. It is what the tool answers with for Bettas, Guppy, Endler's Livebearer, Platy, Molly, Swordtail, Tetras, Danios & Minnows, Rasboras, Barbs, Catfish, Loaches, Goldfish, Cichlids, Gouramis, Shrimp, Pufferfish, Rainbowfish and Snails: every kind in this category without a table of its own.

Safe

Fine, smooth sandCorrect for corydoras, kuhli loaches, eartheaters such as rams and acaras, and anything else that sifts or burrows. Barbels wear away on sharp gravel.
safe
Smooth, rounded fine gravel (not for loaches or sand-sifting cichlids; sand is better for corydoras)Rinse thoroughly before use. Grain size should be too large to swallow and too small to trap food. Kuhli loaches need sand to burrow into and rams and acaras sift mouthfuls of it; bronze and panda corydoras manage on smooth fine gravel, but sterbai corydoras need sand.
safe
Bare bottom (quarantine and grow-out only)Legitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration, and it is no long-term home for burrowing loaches or sand-sifters.
safe

With a caveat

Crushed coral or aragoniteDeliberately raises hardness and pH. Correct for rift-lake cichlids, wrong for soft-water species.
with a caveat
Aquasoil for planted tanksExcellent for plants, but most active soils soften the water and pull pH and KH down for months, and many leach ammonia for the first weeks. Right for soft-water species; wrong for hard-water animals (livebearers, rainbowfish, goldfish, and snails, whose shells erode in soft, acidic water) unless you test GH and KH and remineralise. Cycle around it; do not stock into it.
with a caveat
Very deep sand bedsAnaerobic pockets form below about 2 inches in still sand. Either keep it shallow or keep it stirred.
with a caveat
Painted or coated gravelUsually fine, but coatings chip. Test a handful in a jar for a week first.
with a caveat

Never

Sharp or angular gravel with bottom-dwellersWears down barbels and leads to infection in corydoras and loaches.
never
Anything containing metal, limestone of unknown origin, or shells in a soft-water tankSlowly alters chemistry in ways that are hard to diagnose later.
never

Browse all Freshwater Fish →

Other Saltwater Fish

In a marine system the rock and the sand are life support, and how you start them decides the first six months.

This is the general saltwater fish substrate list. It is what the tool answers with for Clownfish, Basslets, Gobies, Cardinalfish, Damselfish, Tangs, Dwarf Angelfish, Blennies, Wrasses, Dragonets, Dottybacks, Shrimp, Rabbitfish, Hawkfish and Snails: every kind in this category without a table of its own.

Safe

Aragonite sandThe standard marine substrate, and it hosts the biology. It does not meaningfully hold pH or alkalinity at normal reef pH, so test and dose for those regardless.
safe
Dry or cured live rockDry rock avoids importing pests but takes longer to mature. Cured rock is faster and riskier.
safe

With a caveat

Deep sand bedsPowerful nutrient processing when they work and a sulphide release when they are disturbed. Choose shallow or deep deliberately, not by accident. A sand-sifting or burrowing goby needs a fine bed about 2 to 3 in deep that it turns over itself. That is a different thing from a denitrifying deep sand bed (4 in or more, left undisturbed), and the two do not mix: a sifting goby disturbs the layers a deep sand bed depends on and eats the life in it.
with a caveat
Uncured live rockIt will cycle the tank for you, and it will also bring in whatever was living in it.
with a caveat
Bare bottomWorkable in high-flow systems for fish that neither sift nor burrow, but it removes a large part of the biological buffer. Wrong for watchman gobies and other gobies that burrow or sift, which need a fine sand bed at least 2 in deep to dig and feed in, and for mandarins and other copepod-eaters, which need sand as well as mature rock for their food to breed in.
with a caveat

Never

Silica play sandNot the marine standard, and commonly blamed for feeding diatom blooms in a new tank.
never
Any rock or decor of unknown originMetals and phosphate leach for months and are almost impossible to trace once the tank is running.
never

Browse all Saltwater Fish →

More tools

The other five

Is it big enough?

Floor area or volume, judged against the recognised standards: all of them, when they disagree.

Open tool →

Can it eat that?

Staple, occasional, rare treat or never, with the reason. An unlisted food comes back "not on our list", never a guess.

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What does it really cost?

Setup, monthly, first year and lifetime, itemised, with electricity worked out from real wattage.

Open tool →

Which of these two is easier?

Two species on identical axes: space, company, cost, lifespan and daily time.

Open tool →

Is this ammonia reading dangerous?

Free ammonia from your kit's total, the pH and the temperature: the number that actually harms fish.

Open tool →

All the tools → Finding an exotics vet →

Keep going

134 care guides, same data

Every number these tools use comes from the species guides. Read the one for your animal.

Browse the care guides →