A drainage layer is essential to ensure the soil does
not become waterlogged. Scoria, a gardening
product made up of crushed volcanic rock, can be
spread across the base of the enclosure to a depth
of approximately 3-5cm. Other products such as
hydro-rocks (clay balls) and egg crate can also be
used to create the drainage layer. A thin layer of
fine shade cloth or mesh can then be placed above
the drainage material to prevent the substrate from
mixing through, whilst still allowing water to drain
from the soil. Some keepers install a tap and valve
system so that excess water can be removed,
rather than sitting in the base of the tank and
becoming stagnant, however, this involves cutting a
hole in the glass and siliconing in a tap. It is crucial
not to over-water the system, as water build up in
the soil will quickly kill off the plants.
All substrates used in a bioactive system must be
completely organic, with no fertilisers, chemicals or
water retention crystals. A good tropical soil mix can
be made up from 80% organic potting mix and 20%
coco peat. Arid substrate can be created using 50%
sand, 40% organic potting mix and 10% coco peat.
A thin layer of horticultural charcoal can be
sprinkled between the drainage layer and substrate
mix to assist in minimising bacterial
build up and foul odours. The soil
mix should be filled to a depth of at
least 15-20cm, or even deeper,
depending on which plant species
are to be grown. Layers and
mounds of soil can be created,
using rocks and timber as ‘retaining
walls’ and adding depth and detail
to the enclosure layout. A layer of
leaf litter can also be spread on the
surface of the soil. Over time the
soil will compact, and every 6-12
months a bio-revital