Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Substrates for Reptiles: Caveat Emptor

©2000 Melissa Kaplan


There appears to be a lot of choice out there in substrates marketed for reptiles. Fortunately, the decision making isn't so difficult, once you realize how dangerous or inappropriate so many of them are for your reptiles.


Clarification of Terms
The labels the product manufacturers use to tout the supposed safety and desirable qualities of their products unfortunately bear little relation to the reality of the nature of the material and form their products take.

"Digestible" Substrates
There is little difference between those substrate products that claim to be "digestible" vs. those that are indigestible. 'Digestible' means that which can be safely broken down and nutrients extracted; 'indigestible' is that which cannot be broken down. Indigestible matter may or may not be able to pass through the intestinal tract to be eliminated with the waste products. If it doesn't pass through, it can form an obstruction in the gut, one which may eventually block the passage of ingesta or, if farther down the tract, can prevent feces from being passed through to elimination.

Indigestible matter can also puncture or abrade the gut lining, causing perforation, sepsis, or inflammation. All wood, paper, sand, litter and cob products are indigestible, regardless of the fact that they were created from organic (previously living plant) sources.

"It's Natural! It's Biodegradable!"
Disposable diapers are takes, what, 300 years? Orange peels are also biodegradable - they only take 5 years when exposed to the elements. Biodegradability is *not* an appropriate criteria when deciding on a substrate in so far as using it as a measure of safety for the species.

CareFresh is a wood product...and consistently causes respiratory infections in prehensile tailed skinks. I've also noticed that water in snake enclosures evaporate faster when this bedding is used than when I use pine shavings. Shavings, wood and paper pellets have caused and will continue to cause intestinal blockages in reptiles of many different species...just because it is "natural" (wood) or "biodegradable" does not mean, as product manufacturers and pet stores imply, that they are safe for use as substrates... If that line of reasoning were true, there'd be no cause for concern with our iguanas eat things like coins (metal biodegrades), balloons (latex is natural), oleander (it's a plant and iguanas are herbivores, right?).

Bottom line: pet product manufacturers have one primary goal: their bottom line, not the health of your pet. You must become a proactive consumer and learn to ignore the hype and marketing department's hyperbole and half-truths, and evaluate the product itself.


Examples of Problematic Substrates

T-Rex touts their Calci-Sand as a calcium supplement. Unfortunately, this is harmful for most reptiles, such as green iguanas, as if they do ingest it, it will cause impactions, just like all other particulate substrates. Desert animals who live on sand don't ingest enough of it to make it worth the expense, not when plain, cleaned playground sand can be purchased for about $5 per 50 pound bag. Bottom line: The way to prevent metabolic bone disease is not by dumping a bag of an overpriced, potentially harmful, substrate into their enclosure, but to provide a proper calcium supplement for those species who need it; feed a properly constructed and supplemented diet to herbivores and omnivores; feed healthy prey to carnivores, omnivores, and insectivores; and provide UVB-producing fluorescents or direct unfiltered sunlight to those species dependent on UVB for the formation of pre-vitamin D for adequate calcium metabolism.

Zoo Med's Repti-Bark and other bark products are indeed "an all natural product made from the ground bark of fir trees." They do not, however, make a "perfect cage substrate for all high humidity loving reptiles [including] Iguanas, Anoles, Hermit crabs, Tarantulas, Toads and many types of Geckos." Just ask all the iguana owners whose iguanas have died from ReptiBark gut impactions, or were saved by having the vet cut them open and remove clumps of bark from their intestines.

Sani-Chips, Bed-a-Beast and Bedding Bark
These have the same problems: they are wood and so are not suitable for many reptiles, despite manufacturer and seller claims. The most hysterical claim, if one can find such things amusing, is that they are "sanitary" (due to being heat treated) and "mite-free". Well, everything is mite-free until it is exposed to mites! There are no manufacturers out there intentionally impregnating their particulate substrates with mites. That happens in pet stores when the stores accept mite-infested animals from their wholesalers, distributors or from people walking in off the street. The mites, which generally proliferate under the inattentive/uncaring eye of the pet shop employees, start doing what mites do: wander around and breed like the tiny arthropods they are. Within a few short weeks, all wood products within mite strolling or hitchhiking distance has been colonized by mites. Buy the wood product, and you have now colonized your reptiles' enclosures with them. As for sanitary, they are sanitary only until they are wetted by food, urates, feces, or blood. If you don't clean the enclosure regularly, including disposing of soiled substrata and cleaning and disinfecting the enclosure surfaces, it doesn't matter how sanitary a substrate is when it starts out.

Walnut Cob/Walnut Litter/"Desert Sand"
Many years ago, bird keepers became aware of the problem associated with using walnut shell litter for their birds: shortly after being wetted with water or feces and urates, a colony of bacteria started growing, often underneath the surface of the litter. So, what happened when the walnut shell recyclers found they'd lost a significant share of the bird market? Repackaged their crushed shells for reptiles, of course! One went one step farther and touted theirs as safer than sand. Given that I've never seen sand get moldy, that's a pretty odd claim to make. Why is walnut shell (and corn cob, for that matter) not suitable for reptiles? Aside from promoting bacterial and fungal growth (yes, even when they have been "heat treated" at the factory), they can stick to the hemipenes/cloacal tissue when it is everted during defecation and are thus retracted up into the body, causing irritations and inflammation. They also cause irritation, inflammation or injury to the digestive tract if ingested intentionally or accidentally - and no matter how closely you watch your reptile, you aren't watching it 24/7. If that reptile is an arboreal lizard who spends a great deal of time investigating new things with its tongue, ingestion is guarantee.


Particulate Litters = Particular Problems
Another problem with particulate litters in general is that clumps of feces/urates/litter tend to get buried under a layer of litter in the course of the reptile moving around its enclosure, so the moldy clumps may not be found for a while...leaving the reptile to come into physical contact with it, which helps break it up and create airborne spores or particles which are then inhaled, or infect tiny skin defects, or get into the eyes, all of which can cause inflammation and infection.

Some litters, like the CareFresh, are so dusty all the time that many reptiles develop respiratory infections within 24 hours due to the inflammation caused by the inhalation of dust particles. Prehensile-tailed skinks are particularly prone to this.

For a less inflammatory look at substrates and appropriate uses of, please see the Substrates for Reptiles article.


Substrates for Green Iguanas and Other Large Arboreal Lizards


easiest of all to clean and disinfect

Terry cloth towels

cheap to get, can be machine washed with bleach

Paper towels

not as 'green' environmentally, but safe and easy

"Astroturf" (Indoor/Outdoor artificial grass carpeting)

can be cheap but wears out and kind of a drag to clean and\par disinfect when you get into big pieces

Butcher or Freezer paper

a bit slippery when wet but not as fumy as newsprint or newspaper. Available at restaurant supply houses.

Unprinted newsprint

can actually be pretty expensive if purchased at moving supply store; may be obtained in remnant rolls from newspapers. Less toxic than printed newspaper

Alfalfa pellets

safe edible, the only truly digestible particulate substrate, but sometimes dusty; wetted portions must be removed ASAP as it gets moldy very quickly in warm iguana enclosures

Do not use ANY particulate matter, including those new lizard litters and bark products which claim to be safe for iguanas...they are not. No sand, gravel, rocks, cat litter, paper litter, any kind of litter corn cob, shavings, bark, "calcium sand" or sand of any kind.

Related Articles

Substrates for Reptiles (Excerpt from Master's Thesis)

Constipation in Reptiles

Constipation and Diarrhea in Green Iguanas

Use of Laxatives in Reptiles

Use Of Cedar Or Pine As A Substrate

More on the use of pine in captive herp environments


Calcium Substrate Considerations

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