first signed on.
This is what I've dug up from the internet, and I have bookmarked ever since:
Safe And Effective Substrate Mixtures For The Vivarium
Terrariums & Vivariums
The terms terrarium and vivarium are often used interchangeably, or to differentiate between a terrestrial habitat and a semi-aquatic one. Technically, there is a more fundamental difference separating the two. The term terrarium should be applied to an enclosure meant only for the life and the propagation of plants, such that the substrate, lighting, and other environmental conditions are tailored to meet the requirements of specific species. A vivarium, on the other hand, is an enclosure meant to house animals or invertebrates, with environmental conditions suitable for the life and propagation of the particular species. Specifically, vivariums are enclosures for reptiles, amphibians, and other smaller animals and invertebrates that require an earthen or aqueous environment. There are many types of vivariums, such as aquatic enclosures (aquariums) and bog types (paludariums), collectively referred to as vivaria. There are further divisions to each type of vivarium, such as arboreal, fossorial, desert, wetland, shoreline, cloud forest, etc., that are designed to meet the needs of the particular inhabitant.
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
Beneficial bacteria is one of the most important elements of the substrate, as it maintain the nitrogen cycle by breaking down organic matter into "plant food", and helps fight and prevent the spread of harmful pathogens that may be brought in on the inhabitants. Without a descent supply of nitrifying bacteria, organic matter will not break down, instead rotting at the surface and turning into toxic materials, and harmful pathogens may run rampant throughout the substrate. The latter often causes serious health problems with imported animals carrying potentially deadly pathogens. Such animals are usually stressed upon arrival, which can weaken the immune system, and putting them into a sterile enclosure, where harmful pathogens can spread uninhibited, is often a major cause of death.
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.
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 [or EE]
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 (EE) 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).
says, I think the 5 parts sand, one part coir (EE) helps in the ease of digging, plus with the added benefit of being able to possibly allow beneficial bacteria to grow like as in the sandy soil in the wild around the forest beach areas where wild hermits live. I remember seeing wild ruggies around where the forest meets the beach areas, and the surrounding soil was essentially being mixed together with sand - so I suppose one way of simulating this is to add a bit of EE into sand (short of actually adding real soil into your sand - ideally this is what I'd do, if it weren't for the fact that I'm not really too confident of the soil around where I live, so I guess it will be EE then...)
Adding EE also has the benefit of taking up more volume (for the crabs' burrowing needs) but not adding as much weight if it were just pure sand.
Currently, my substrate mixes with EE has had fewer (if any) of those noxious dark spots (bad, stinky bacteria, I suppose, for lack of a better term) when just using plain sand in the past and the hermit crabs buried any uneaten food. I guess the "beneficial" bacteria (when mixing sand with EE) does inhibit a bit of the "bad" bacteria from growing when the hermits bury food or poop....
This is what I've dug up from the internet, and I have bookmarked ever since: