Last update: July 30, 2004
Aquaponics is the blending of aquaculture (fish-keeping) and
hydroponics (growing plants without soil). In an aquaponic system the
fish, plants, and various bacteria form a symbiotic group: the fish eat food and
excrete waste. The fish waste is consumed by the bacteria which break it down
in to nitrates, which are absorbed by the plants. This cycle helps clean the
water of waste products, which keeps the over-all system habitable.
Established December 6, 2003
Here is an image of a small aquaponic system prototype. This system consists of
a 10 gallon capacity aquarium, equipped with a heater and power filter, and a
grow bed mounted above the tank. The grow bed is filled with epoxy-coated
aquarium gravel (chemically inert), and is fed aquarium water by a small pump
salvaged from a table-top foutain. The water is distributed into the grow bed
by a tube with multiple perforations buried just below the surface of the gravel.
Another perforated tube sits on the bottom of the bed, and is connected to the
return tube which drains the water back into the aquarium.
In this system the aquarium is stocked with one plecostomas and three neon
tetras. The water temperature is kept between 76 and 78F. A timer runs the
aquarium lights for 10 hours per day. The fish are
fed flake food once per day, and the pleco also grazes algae that grows
on the tank walls. The grow bed was planted with a single cutting from a
The choices of inhabitents for this experimental system were mostly what was
available. The aquarium was well established, having run for about three
years before the grow bed was added. The plant was a cutting from one
growing in a pot in the office. The philodendron is not a bad choice, since
it is hardy, doesn't require much light, and cuttings will root in water.
In most aquaponic systems the choice of species
is made to insure compatibility with each other and their environment. In this
specific case, the system is mostly ornamental and is exposed to moderate indoor
light levels. A commercial system for producing food fish and crops would
obviously require different species, and would be optimized for maximum
production rather than asthetics.
Update: Feb 24, 2004
The inital system is working well. The water flow through the grow bed has been
somewhat problematic: sometimes the water doesn't flow out quickly enough, and
the bed fills to within a couple of inches from the top with water. This
happened on and off for a few days when the system was first set up, but then
started working properly, keeping only an inch or so of water in the bottom.
When three more plant cuttings were added to the system, the water once again
started doing its weird non-flowing bit, but after leaving the pump unplugged
overnight, the system worked properly again the next morning. This may be
due to a too-small pipe or opening for drainage back into the tank. While
changing this would be somewhat of a pain, another possibility being
considered is adding a larger overflow pipe higher up on the bed. This would
allow water to be routed back to the tank in case the drain line 'plugged'
again in a controlled fashion, instead of possibly overflowing the bed
container which would make a mess and also possible allow the pump to empty
In any case, the original plant cutting is quite healthy, although growing
more slowly than expected. The two new cuttings were made from the same
Update: April 4, 2004
The water level in the growbed continues to fluctuate. When the level
in the tank gets too low, water is added directly to the bed. The water then
flows down the drain into the tank and replenishes the system. For some
odd reason, this always seems to cause the water level in the growbed to
stay high, even after the pump is unplugged, all the water drains out, and
the system is even left this way overnight. I'm speculating that there is
either something in the drain tube that gets disturbed and partially plugs
the drain holes (maybe a bacterial film), or it could be something as
simple as the pump being able to produce more pressure when the tank is
full vs. low. In either case, the high level in the growbed causes
concern that the water might spill over the edge and onto the carpet.
To prevent this, the pump has been left unplugged overnight on several
Two of the new plant cuttings had their stems die and had to be removed
from the system. If this was due to drying out during the pump-off
nights, or they just didn't root properly is unknown. The original
cutting looks very healthy, and one of the new ones looks ok for the
I plan to switch to a larger diameter drain tube in the near future to
try to alleviate the level problem in the growbed.
Update: July 16, 2004
The aquaponic system has been disassembled. The growbed drainage problem
never did get solved, and while the original plant flourished, four
additional cuttings died. The high water level in the growbed was a
continual source of concern, and lowered the water level in the aquarium
enough to cause problems with the filter and heater. The whole system
also wasn't, well, all that nice-looking. I opted to leave the growbed
support platform on the tank and use it for potted plants to improve
the appearance of the tank.
This is not the end of my aquaponic experiments, just this first version.