_PRESENT DESIGN OF THE VENTILATED TERRARIUM_
April 1994, Brian A. O'Brien
ENCLOSURE
This enclosure is constructed from a large rectangular glass tank,
the joints of which are held glued. This was at one time used as
a water bath for chemical kinetics experiments. I had only to lie
in wait until its owner decided to junk it :).
The terrarium is roughly 2 feet deep (top to bottom) X 1 foot
(front to rear) X 2 feet wide (side to side). This terrarium is
all glass, but this shouldn't be necessary - I plan to build future
terraria with glass only in the front, top and/or sides.
The top is a sheet of glass with corners cut off to accommodate air
and water inlets (described below)
MEDIUM FOR LOWER REGION
The bottom layer is lava rock (the kind which is sold for mulching
plants) and charcoal briquets (about 1:1 mixture), about 6-8 inches
deep in the rear and about four inches deep in front - the slope
is for a landscaped effect.
Approximately four inches of a mixture of peat and vermiculite,
with some Perlite, covers the lava rock. This layer is covered
with a layer of sphagnum moss.
EPIPHYTE MOUNTING SYSTEM
The epiphyte mounting system is constructed of PVC water pipe
thickly covered with absorbent materials. Two vertical 3 inch
diameter pipes with tee connections stand in the rear corners; they
are connected by a 3/4 inch pipe which has a branch at
approximately 2/5 of its length. The branch extends toward the
front of the terrarium, bends to one side for a short distance,
then curves down to rest on a flat rock. The end of the branch is
capped, as are the bottoms of the 3 inch pipes (these by a flange
joint with an insert). All joints are thoroughly sealed with
silicone sealant.
The pipes are first wrapped with polypropylene lawn fabric which
holds a thick layer of fine vermiculite and tied in place with
nylon string. A thick layer of wet sphagnum moss is then tied
around the entire object by use of fishing line.
The epiphyte mount is prepared for watering by judicious drilling
of holes into it while it is filled with water. (Note: the
polypropylene cloth tends to wrap around the drill bit.)
After placement of the structure in the terrarium, I mount
epiphytes by cutting U-shaped lengths of nichrome wire and
inserting these into the moss layer. These can be removed and re-
used when (or if...) the plant becomes established.
LIGHT
Four Gro-Lux Wide Spectrum tubes irradiate the top of the epiphyte
mount, through the glass, from a distance of approximately six
inches. Excess fluorescent tube length extends over a filing
cabinet which is home to some Euphorbias.
WATERING AND FERTILIZING
Watering is done through a funnel, connected to one of the 3 inch
PVC pipes by 3/4 inch corrugated plastic sump pump hose. I use
deionized water, often with about 10% tap water added. Fertilizing
is done either thorough the water (Dyna-Gro) or by pouring or
spraying (fish/kelp or kelp solution). A hole was drilled in the
bottom of the front panel of the enclosure for drainage - this is
done through a clear plastic hose sealed into the hole by silicone
sealant and protected from plugging by a wad of polypropylene
pillow batting.
VENTILATION AND HUMIDITY
The enclosure is alternately ventilated with pre-humidified air and
moistened by a room humidifier. The fan turns off when the
humidifier turns on (otherwise the moisture is dissipated) - this
is controlled by a relay (for alternating current, available at
Radio Shack).
The humidifier comes on four times daily (30 minutes, 15 minutes,
5 minutes, 5 minutes), and is controlled by an electronic timer.
It is connected to the terrarium near the top, so as to have the
fog spill over the epiphyte mount. Only deionized water is used
in the humidifier (distilled water would be even better). The
region to the far side of the mist inlet remains considerably more
dry than the region in direct proximity to the mist.
Air for ventilation is pre-humidified by passing it through a
reservoir of water. The reservoir is a large (about 10 gallons or
so, made for storage of clothing, blankets, etc.) clear plastic
storage container (Target, Wal-Mart, etc.) filled with lava rock
for increased surface for evaporation, fitted with three PVC
fittings for 3/4 inch hose mounted in the top, and sealed with duct
tape. A small blower forces a stream of air into one corner of the
tank, and air exits through the corner diagonal to the inlet. The
third fitting is plugged with a cork and is used for refilling.
All air connections are made with corrugated plastic sump pump hose
sealed with duct tape. (The sump pump hose is _very_ cheap
compared with other types of tubing.) The inlet into the terrarium
vents air through two PVC fittings in the rear, at the soil layer,
placed at intervals of about 1/3 of the total length of the
enclosure. One of them vents through a tent of glass plates so as
to come out nearer the front and prevent excessive drying of the
epiphyte mount.
GENERAL COMMENTS
The enclosure dries out _much_ faster if the air is not pre-
humidified. I water it about once per 7 to 10 days during the
driest parts of the year (this is usually winter, due to the
horrendous overheating of our building). It is important to keep
watch on plants which are not established - they can dehydrate more
rapidly than one might think. After the roots have penetrated the
mount, the plants are much more robust.
Fungus diseases are minimal and those which have developed have
been easy to control, for the most part. Animal pests encountered
are scale, mealybugs, snails, and sowbugs. These have all been
relatively easy to control, with the snails and sowbugs being the
most tenacious.
bobrien@hermes.gac.edu
Brian O'Brien tel. (507)933-7310
Department of Chemistry fax (507)933-7041
Gustavus Adolphus College
800 West College Avenue
Saint Peter, Minnesota 56082
U.S.A.