Substrates

 Substrates do many things in a tortoise habitat: 

  • make it look better for the viewer, 
  • make it easier to keep clean and maintain,
  • encourage natural behaviors, like digging,
  • provide good traction for the tortoise,
  • keep the tortoise healthy (as in preventing impaction, low dust, etc.)
  • help regulate humidity
  • provide some warmth from beneath.

Many people have differing thoughts about substrates for forest species:

Bioactive Substrate Systems

Pioneered by Philippe de Vosjoli’s “The Art of Keeping Snakes”, from Advanced Vivarium Systems, a “bioactive substrate” is a mini-compost pile designed to help maintain high humidity and break-down feces and food wastes. While there are several ways to approach this, the basics are to use layers of materials.

  • First, an optional inch of coarse material like broken lava rocks offers “air space” and attachments points fo good bacteria to colonize.  This is not needed for tortoises or if space, thickness, or weight is an issue.
  • About 4 inches of a good soil mix like those in the “Soil Mixes” section below, with plenty of sand or clay cat litter, wicks moisture from the bottom to create humidity above, and provides a home for micro-organisms that will break down wastes.  Prevent compaction by using thicker layers for heavier tortoises, and by adding mosses, wood chips or similar substances.
  • A top layer of moss, shredded cypress, palms leaves, or other materials keeps the tortoises dry and clean but allows humidity to rise past it. (“Top dressing” also makes it harder to stir the mixture.  I usually skip it.)
  • Besides the layers, other key elements include:
        ◦ A method to check water levels and add water as needed, like a simple tube reaching down to the
    bottom.  There should be about 1/2″ of water in the bottom at all times.
        ◦ Adding earthworms and isopods (“roly poly bugs” or wood lice) will help fight pests like   fungal gnats and break down wastes, and adding some good, rich compost will provide all the micro-organisms you need.
        ◦ Live plants add humidity, micro-organisms, and help remove the waste by-products from the soil.
    Tortoises generally eat or trample live plants, but they can be in pots, have protective rings around them, etc.

Hardwood Mulches

Probably the easiest and cheapest general purpose substrate for many forest chelonians is a few inches of hardwood mulch or chunks such as cypress, orchid bark/Douglas fir bark, coconut coir or nuggets. Pouring water in a hardwood
mulch results in a puddle on the bottom that can then rise as humidity. Additional benefits include reduced “dirtiness” and fewer pests, although plants cannot be grown in it easily.

  • I prefer cypress mulch or whatever the common landscaping mulch is in your area. The large bags are usually an economical choice. Avoid ANY mulch that has dyes; chemicals; rubber bits; or smells of chemicals, cedar, pine, or manure
  • Some of these mulches, such as coconut coir, benefit from adding some sand to help with drainage and to keep it from compacting.
  • RussianTortoise.org recommends a mix of 3 parts coconut coir (Bed-A-Beast, etc.) and 2 parts sand (by weight) for forest species.   

[Author’s note- I have used this basic mix in my indoor habitat, and was very happy with it, although it can harbor pests as well.]

Note:
Many sources state that pine is harmful in some ways to many animals, but there is little evidence that pine bark nuggets are a concern. Once again, you should avoid any mulch with a strong chemical, pine, cedar, or manure odor; or that contains chemicals, dyes, or rubber chunks.

Soil Mixes

Various mixes of soil components are recommended by Tortoise Trust and others (proportions are averages of several formulas):

  • 2 parts sand (“soft” or play sand), to prevent compaction and allow some drainage.
  • 2 parts loam compost, clean topsoil, etc. for moisture and to burrow into.
    (Note: Avoid soils with bad smells, or small white pellets in it.)
  • 1 part sphagnum moss, shredded bark, coconut coir, etc. for moisture, and a “binder”. Aim for at least a 2in layer for young tortoises, and about 4” for adults.

[Author’s note: This is a good and cheap mix, but aim for a soil that has no smelly manure. Damp substrates like this can harbor springtails and fungus gnats.]z
[Note 2- If you are going to do this, you may as well make it a “Bioactive Substrate” as described above.]

Tortoise Trust also offers the idea of using wide flat pans in a tortoise table with a variety of substrates such as a pan of pebbles or a pan of growing plants. 

Soil-less Rainforest Substrate Mix

Reptiles Magazine had several mixes for indoor habitats with live plants. Here is the recipe for rainforest/tropical set-ups:

  • 2 parts partially composted leaves (leaf litter from a compost pit or around the base of a tree.  Tough leaves make the best material: alder, elm, poplar, apple, or ash. (Oak is good but toxic to many animals).
  • 2 parts medium grade Orchid bark, fir bark, “Xerimulch” or similar materials
  • 1 part ground coconut husk fibers or coir (can include up to 1/2 part of shredded palm)

Moisten and allow to “rest” before use.

Fertilizer for this mix, added to 1 gallon of water:

    • 3 tablespoons cottonseed meal
    • 1 tablespoon bone meal
    • 1 tablespoon blood meal
    • 1 tablespoon “Ironite” or other iron source
    • 1 heaping teaspoon ‘agricultural lime’ (crushed oyster shell, etc.) 

Other substrates

Sphagnum moss
Long-fibered sphagnum moss, can be teased out and dampened to make a high-humidity substrate that is especially helpful for smaller tortoises and turtles. The very acidic moss prevents fungi and pests.

Newspaper, corrugated cardboard, or paper towels
These are generally used mostly for “hospital” or clean settings, but some experts recommend them for everyday use to maintain a cleaner habitat. Corrugated cardboard (flat on one side, corrugated on the other, often available at craft or packing stores) is about the best compromise between cost, cleanliness and traction. Newspaper alone is so slippery that growing tortoises have problems walking on it and it can affect the development of the leg bones.

Other substrates have pros and cons, but generally are not satisfactory for our purposes: carpets, hard surfaces, plain sand, rabbit chow, kitty litters, paper-based litters or liners. 

Whatever substrate you use, it should be spot cleaned as needed: removing feces, or any evidence of fungal growths. The substrate often benefits from some stirring up. Substrates can also go “sour” over time, picking up odors, breaking down or compacting,  and will then need to be replaced. 

 IMPORTANT:

Red-footed Tortoises seem very susceptible to some form of plastron rot if they remain in contact with damp substrate. Aim for substrates of a type and depth that you can keep the bottom layers wet, but let the top layer stay dry. The pH level of the substrate may affect this as well, especially with substances  like sphagnum moss.

Substrate Improvements

No matter what substrate you use, there are things that can make it better. A deep substrate (6 inches or so) helps a closed or semi-closed system regulate itself. The deeper layers hold water down deep and absorb heat. When the air above it gets cool or dry, it will “steal” it from the substrate and try to equalize itself.

  • Tom Barthel, (“The Hydration Equation” Reptiles, July 2007) suggests adding a top layer of shredded bark, leaves, or moss to a soil-based substrate. This helps trap moisture under it which would control humidity, makes a nice burrowing layer, helps keep things clean, and adds to the overall look. Personally, I find “top dressing” adds to the amount of work it takes to keep things nice.
  • Warming the lower levels of a substrate will heat the water, which will result in increased temperatures and humidity in the habitat. This is a great technique to use in cooler climates or in a cooler home. You can do this with items like greenhouse soil warming cables or Flex Watt tapes. Be sure any heating elements used are being used per instructions. You can also heat the space under the habitat to accomplish this.
  • Hermit crabs, along with earthworms and isopods (wood lice) can help clean wastes, and add other benefits. Hermit crabs are interesting animals themselves.
  • Flat landscapes are boring to viewers and tortoises. Whenever possible, sculpt or build hills, slopes, caves, etc. into the substrate, just make sure that if a tortoise flips on it, it can right itself.
  • Offer a variety of surfaces to walk on. Many people have luck making features like pebble walkways, seedling trays of grass, etc.
Additional ResourcesBioactive Substrates at GeckoTime
Substrates at Anapsid.com
Risks of Cedar Substrate at Anapsid.com
Soil Mix for Terraria at Chelonia.org
Terrarium Construction at AmphibianCare.org