At determination of conditions of keeping tarantulas in captivity follows to take into account that substratum in terrarium is not only "bedding" for it, but executes also as minimum two most important functions - maintenance of general humidity/moisture and provision of molting process. In nature a spider, moving deep into burrow or, on the contrary, to its surfaces, wresting lateral tunnels or deepenning the burrow, thereby adjusts temperature-humidity mode. In captivity when making and regulating of conditions artificially directly by keeper, such role of substrata for adult tarantulas goes to minimum, but for tarantulas of early ages exceedingly essential.
On the grounds of perennial experience of growing spiderlings is noticed that at presence of big layer of moistened substratum, as a rule, problems with molting does not appear and also, practically, the possibility of dehydration is absent.
There`re different opinions exist amongst tarantula keepers around the world about composition of substratum and the material used as substratum. However absolutely clearly is possible to formulate the requirements, which it must without fall be correspond to – hygroscopy, i.e. ability to absorb sufficient amount of water and slowly vaporize it, neutrality (not aggressiveness of ambience) and hygienic. Hygienic of substratum is concluded in as possible greater its stability to rotting and defeat by funguses, as well as suppress of duplications of mites in it.
To the presented requirements, certainly, is corresponds vermiculit. This is mineral sort, broadly used in hydroponic culture under growng agricultural and decorative plants by intensive way. Vermiculit is chemically neutral and has antibacterial characteristics. The only its defect is concluded in that it presents itself small faction, molders and for this reason can be not used for keeping actively digging species.
The other substratum on which tarantulas can be kept successfully is turf and its different mixtures, and as most practical - mixture with peatmoss in different proportions. Such substratum also possesses high hygroscopy but much easier infected with fungus and, being biologically active, requires its significant thickness in terrarium which does its more practical for digging tarantulas.
Remember that under most slightest manifestation of growing of funguses or appearance of mites in terrarium it is necessary immediately to change the substratum and desinfect it!
It is also stands to pay attention to such exotic for present-day in Russia a type of substratum, as small milled coco filament, broadly used by amateurs in Europe. It corresponds to all presented requirements to substratum for keeping tarantulas but not wide-spread while in sale in Russia.
In the last resort it is possible to use as soil flower-potted ground, but in conditions of increased moisture required for all tropical species, there`re much greater danger of mites and funguses development.
Do not recommended to use as a substratum for tarantulas gravel, as well as artificial covering. Thickness of layer of substratum is important for digging species as (Hysterocrates spp., Haplopelma spp. some others). For other tarantulas its must suffice for maintenance of humidity/moisture, i.e. 3-7 cm depending on substratum type (less for vermiculit, more for earth-based substratum).
Remember: in no event it`s impossible allow to overmoist a substratum – this can kill the spider!