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 attachment points for good bacteria
  to colonize. This is not needed for tortoises or if space, thickness, or weight is an issue.
• About 4in
  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, etc. 
• A
  top layer of moss,
  shredded cypress, palm 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, etc. 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 ½” of water in the bottom at all times.
• Adding earthworms and
  isopods (‘rolly polly 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- cypress, orchid
bark/Douglas fir bark, coconut coir or nuggets, etc. 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 few
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- but
  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.]
  
• [Note 2- If you are going to do this, you may as well make it a
  ‘Bioactive Substrate’ as described below.]
• Tortoise
  Trust also offers the idea of using wide flat pans
  in a tortoise table with a variety of substrates- a pan of pebbles, a
  pan of growing plants, etc. 

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, ash, etc. (Oak is
  good but toxic to many animals.)
• 2 parts medium grade Orchid bark, fir bark,
  ‘Xerimulch’, etc.
• 1 part ground coconut husk fibers or coir (can
  include up to ½ 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, as discussed at sites like Turtletary.com, 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, etc. 

Whatever substrate you use, it should be spot
cleaned as needed- removing feces, any evidence of fungal growths, etc.
and often benefit from some stirring up. Substrates can also go ‘sour’
over time, picking up odors, breaking down, compacting, and so forth
and 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 things 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 things 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 things like pebble walkways, seedling trays of grass, etc.



Additional Resources

• Reptile Substrates at Dr.’s Foster and Smith
• Bioactive Substrates at GeckoTime
• Bioactive Substrates at HerpFamily.com
• Substrates at Anapsid.com
• Risks of Cedar Substrate at Anapsid.com
• My favorite waterproof heat rope from BigAppleHerp.com
• Soil Mix for Terraria at Chelonia.org
• Terrarium Construction at AmphibianCare.org