Terrariums & Vivariums

For completeness, there are other types of captive environments that do not fall under the vivarium category, such as aviaries and cages.  

Both terrariums and vivariums require a proper substrate with significant biological activity, however, the requirements of the vivarium substrate are a bit more complex. The vivarium substrate must be able to break down organic matter, such as feces, shed skin, and uneaten food. It must be able to maintain a variable degree of moisture, without clumping, turning to mud, or drying out, and cannot contain noxious or toxic materials, either man-made or natural. The media must also be able to withstand the physical activities of the inhabitants, without significant modification of its composition. It must remain aerated, moist, and nutrient rich, and must not only house, but maintain a healthy colony of beneficial bacteria. A good substrate can last for years in an enclosure, and is a necessary requirement for healthy inhabitants. All too often poor substrate results in unhealthy captives, death, or at the least, constant reconstruction of the enclosure.

Most all substrates smell earthen when first laid down, but after a while, a bad mixture will develop a sour, rotten smell, indicating the need for replacement. This is common in many vivaria, and is an indication of poor soil mixture. It may be too wet, with pockets of stagnant water where bacteria and fungi have built up, or it may lack nitrifying bacteria required to break down organic matter. Some substrates settle after a while, becoming hard and packed, and drying out easily. A good mixture will smell fresh and earthen for years. 

A Note About Beneficial / Nitrifying Bacteria

Bacteria are introduced into the enclosure via materials collected outdoors, from healthy environments. In the forest vivarium, decomposing leaf litter serves to introduce a starting colony of bacteria. In the bog-type vivarium, this is accomplished by the addition of fine silt from an natural pond, or by adding of portion of substrate from an established aquarium (see the recipes below for more info).

Substrate Ingredients

• Leaf Litter
  Decomposing leaf litter from a non-polluted forest is an essential element in any healthy vivarium substrate. Natural leaf litter not only adds texture and nutrients to the mixture, but also introduces beneficial bacteria and fungi. In addition, small invertebrates are inevitably picked up in the leaf litter, which add to the biological activity of the media, and can serve as potential food sources for the inhabitants (depending on the species).
  
  In non-trafficked forests, fallen leaves pile up around the bases of the trees throughout the changing seasons. At the top of the leaf litter will be the most recent layer, which should consist of whole, newly fallen leaves, in an early stage of decomposition. The lower layers are more decomposed, with the very bottom layers turning dark brown or black, and taking on a crumbly, soil-like composition. Materials from the top layer, all the way to the bottom layer, where the leaf litter meets the ground, should be used in the natural vivarium. Simply put on a pair of gloves and fill up a bucket, as needed.
  
  Stiffer types of leaves are preferred, such as scrub oak, alder, elm, birch, aspen, poplar, beech, apple, ash, holly, and privet (Searcey, 2001). Avoid using soft leaves, such as maple, mulberry, sweet gum, magnolia, and tulip tree, as these will turn to mush as they decay (Searcey, 2001). Also avoid noxious species, such as eucalyptus, oleander, melaleuca, pepper, bottlebrush, and brugmansia (angel's trumpet) (Searcey, 2001).
  
  Make sure the spot of collection is not chemically polluted, otherwise serious health issues can arise in the captive environment. Many parks are sprayed with insecticides several times a year to kill off wasps, bees, ants, and other picnic invaders. For this reason, parks and other recreation spots should be avoided as much as possible.
  
  
• Coconut Husk/Bark
  Coconut husk is often available in the form of cubes, irregular chunks, or fiber (coir). The larger, chunkier types play an important role in drainage, and aeration of the vivarium soil. These should be mixed into the soil medium in moderation, as too much coconut material can lower the pH of the soil too much. This may be desirable in some cases, but many species are susceptible to highly acidic substrate, so always check the requirements of your captives first. Coconut cubes chunks take an extraordinarily long time to break down, and so will remain intact for years in the vivarium.
  
  
• Compressed Ground Coconut Husk Fiber
  Coconut husk is often ground and sold in compressed blocks that expand into a fluffy material when soaked in water. Coconut fiber, also called coco-fiber or coir, serves as a "filler" in the medium, and also aids in moisture retention. Coconut fiber should be used in place of peat moss because it lasts much longer, is less acidic, and does not inhibit the growth of bacteria (Searcey, 2001). Coconut fiber is also more environmentally friendly than peat moss because it is harvested from farms, whereas peat moss is taken from the wild.
  
  
• Ground Palm
  Ground palm serves the same purpose as coconut fiber, that is, to create a light, moisture-retaining material, but also aids in drainage. Ground palm also provides a source of beneficial bacteria and fungi (Searcey, 2001).
  
  
• Orchid Bark & Xerimulch
  Bark is added to the mixture to increase drainage and aridity. Orchid bark is used as a substrate to grow orchids on, and consists of cubed or irregular shaped pieces of bark from various tree species, but often firs (Searcey, 2001). Xerimulch, by Kellogg Co., is a similar landscaping mulch.
  
  Fir bark can be purchased in other forms, and is a good choice for the vivarium because it does not contain toxins or noxious resins, phenols, or sap (Searcey, 2001). Avoid pine, because of its noxious sap, and redwood bark because it contains bacteria-inhabiting properties (Searcey, 2001). Also avoid eucalyptus for the same reasons.
  
  
• Inert (biologically inactive) Sand & Gravel
  Inert sands and gravel are used in bog type vivariums (paludariums). This type of ingredient should be comprised hard, inert rocks, such as granite or hard sandstone (Searcey, 2001). For acidic and neutral environments, avoid materials that raise the pH, such as calcium-containing substances, limestone and other types with high amounts of lime, or soft marble (Searcey, 2001). Also avoid chalky or metallic types, and those with patches or veins of bright colors, such as red, blue, or yellow (Searcey, 2001).

click to enlarge

Substrate Recipes

Forest Floor Mix
This type of vivarium substrate is intended for use with forest- or woodland-dwelling species, and some tropical species. The next mixture recipe, Tropical Floor Mix, is more suited for vivariums with dense tropical foliage, as this type of mixture adds more aridity and better drainage. The Forest Floor Mix should provide a mildly aerated soil that is neither too wet nor too dry. This type should be biologically active, and tough enough to withstand the wear and tear of use by the inhabitants.

In a large container, mix the following with de-chlorinated, spring, or deionized water:
2 parts decomposing leaves, including newly fallen down to highly decomposed layers.
2 parts orchid bark, Xerimulch, or equivalent Fir Bark.
1 part ground coconut fiber (expanded, see below).

optional 1 part sterile vivarium mixture (such as Jungle Mix brand).

The amount of water added will depend on the requirements of the intended species. Some amphibians prefer a mildly moist substrate, while others may need a little more moisture. The brick type coconut fiber will need to be soaked in chlorine-free, spring, or deionized water until it expands into a fluffy medium. Excess water should be squeezed out, until the fiber is just moist to the touch. Remember, you're going to add water to the entire mixture, so the fiber does not need to be soaking wet. Sterile vivarium mix is optional, and serves only as a "filler" medium to create a smoother substrate. Make sure to check the ingredients of these types of pre-made mixtures, as they may contain large amounts of coconut products, which in addition to the coconut fiber already added, may raise the pH too high.

Once the mixture is created, it should be lightly packed into the vivarium. It should not be packed firmly into the enclosure, as it will settle a bit with time. A little compression is fine, though. The surface can be shaped into small or large hills and crevices for a more natural look and feel. Rooted plants, mosses, leaf litter, rotting logs, and whatnot can be added as well, as required by the particular species intended.  

Leaf litter, orchid bark, ground coconut fiber, and sterile vivarium mix in bucket,  after mixing with de-chlorinated water. This batch is ready to be lightly packed into a woodland vivarium.

Tropical Floor Mix
This type of vivarium substrate is intended for use with tropical species that live on rich soils in the wild. The Tropical Floor Mix is virtually the same as the Forest Floor Mix, but with added coconut husk chips. The coconut husk chips provide additional drainage and aridity, which make this substrate ideal for those tropical plant species with such requirements. This type should also be biologically active, and tough enough to withstand the wear and tear of use by the inhabitants.

In a large container, mix the following with de-chlorinated, spring, or deionized water:
2 parts decomposing leaves, including newly fallen and highly decomposed layers.
2 parts orchid bark, Xerimulch, or equivalent Fir Bark.
2 parts coconut husk chips.
1 part ground coconut husk fiber (expanded, see below).

optional 1 part sterile vivarium mixture (such as Jungle Mix brand).

Create the Forest Floor Mix described previously, and add the additional coconut husk chips to the mix.

Once the mixture is created, it should be lightly packed into the vivarium. It should not be packed firmly into the enclosure, as it will settle a bit with time. A little compression is fine, though. The surface can be shaped into small or large hills and crevices for a more natural look and feel. Rooted plants, mosses, leaf litter, rotting logs, and whatnot can be added as well, as required by the particular species intended.  

Bog / Marsh / Shoreline Mix
This type of vivarium substrate will essentially simulate a boggy, shoreline environment, while ensuring proper oxygen circulation. In a bog or marsh type environment, anaerobic bacteria are able to flourish in the oxygen depleted substrate, which in captivity, will lead to deaths rather quickly. The purpose of this type of substrate is to provide a medium that  will be heavy enough to support plants, yet porous enough to allow water circulation. The presence of oxygen in the substrate will prevent the proliferation of anaerobic bacteria, and thus create a healthy bog/marsh/shoreling environment that can maintain animal life in an enclosure. Bog/Marsh/Shoreline type environments are specifically those with land or wetland areas, as well as a water body. Sand or gravel substrate are recommended for aquariums, where there is no land area.

In a large container, mix the following with de-chlorinated, spring, or deionized water:
2 parts inert sand.
1 part ground coconut husk fiber (expanded, see below).
1/4 - 1/2 part fully composted leaf litter.
1-2 cups of substrate from an established aquarium or natural pond.

The brick type coconut fiber will need to be soaked in chlorine-free, spring, or deionized water until it expands into a fluffy medium. Excess water should be squeezed out, until the fiber is just moist to the touch. Sand will need to be rinsed to remove all dust-like particles. Fully composted leaves are preferred with this mixture. These will appear dark and crumbly, and will smell very earthen. These will add a bit of richness to the soil, but will not be serve to introduce a starter colony of bacteria and fungi. The starter colony will come from the addition of a small amount of substrate from an established aquarium, preferably sand, or natural pond. Natural bogs and marshes should be avoided, as these may contain toxins and undesirable bacteria that will prevent a healthy enclosed environment.

A typical bog or shoreline tank can be created by sloping the substrate up on one side of the tank to serve as the land area. The land area can be covered in small cobblestone type rocks of various sizes, that lead down into the water area. On the rocks can be grown java moss or other type of semi-aquatic mosses, and between the rocks can sprout plant life of all sorts. This type of enclosure can be made to stay very wet, or wet in only some places, depending on construction and tank size.

When this type of tank is first constructed, the substrate will continue to soak up water until it is saturated, so be prepared to add water everyday for the first week or so.

What to Avoid

• Potting Soil
  Regular potting soil should never be used, as it typically contains substances/chemicals that may be detrimental to the health of amphibians or reptiles. Also, potting soil is also not meant for enclosures, but for pots with drain holes. Potting soil in an enclosure will pack down and become muddy, and so should not be used for terrariums, either. 
  
  
• Terrarium Mixes & Animal Substrates
  Although many processed substrates sold for terrariums, and even those made for use with animals, are chemical-free, they may also be nearly sterile, lacking a significant colony of nitrifying bacteria. These types of mixtures are usually lacking other important elements as well, such as materials for aeration. Also, because of their fine texture, these types often have moisture problems, either becoming too wet with watering or spraying, or drying out too easily.
  
  Some processed mixes made for use with animals can be included in the final medium, and make good "filler" materials, but should not be used alone with inhabitants in the vivarium.
  
  
• Charcoal / Activated Carbon
  Regular charcoal or carbon, not the activate type for aquariums, does not serve an important function in the substrate of a vivarium. At some point in the past people started using charcoal, including the activated type, in layers of the substrate to remove chemicals. The activated type probably does remove a small amount of pollutants from the soil, but in a healthy environment with a flourishing bacteria colony, the need for additional pollutant removal is nil. Regular charcoal does not serve any purpose in the vivarium, however, some orchid growers use it in the potting mix to aid aeration because it never decomposes (Searcey, 2001). In the vivarium, a substance such as coconut husk cubes would be a better choice, as these add to the richness of the substrate.

References:

Searcey, R. L. "A Little Shoreline Vivarium". Reptilies Magazine, Oct 2001: 42-47.