While tilapia have been raised in pond cultures for millennia, it was only in the last few decades that raceway culture began to be attempted and perfected.  The difference between ponds and raceways were first and foremost control of population and the relative ease of harvesting from a raceway as opposed to a pond.  Ponds often had to be drained completely through large holes built into the walls or dikes of the pond.  These holes held valves, called monks, for ease of operation.  Still, it doesn’t take much imagination to understand the mess that thousands often millions of gallons of water pouring from a pond through a monk into some form of collection ditch or nearby pond can create.  The fish which thrashed into awaiting nets as the water passed through had to be removed quickly in order for the harvest to continue smoothly.  Further, ponds which are not lined with plastic liners offer tilapia an opportunity to display one of their unique and amazing qualities.  An unlined pond drained completely to the mud line is not an empty pond.  In developing countries, these ponds are often drained and the villagers permitted to walk in and gather all the remaining visible fish for cooking and salting, smoking or preserving in some other way.  However, with the next rain, or the opening of a valve to refill the pond, tilapia will appear as if by miracle.  Yet, the miracle is in God’s design.  The tilapia are capable of burrowing into wet mud and breathing, literally extracting oxygen from the moisture in the mud, for great lengths of time.  Fry and fingerlings can survive the longest as their oxygen requirements are the least.  But even larger tilapia will hold out an unbelievably long time.  Thus, if a farmer wants to control his or her pond population (and this is a critical element of being able to supply sufficient feed in an artificial environment), the draining of an unlined pond must be followed by weeks of striving to ensure the death of all remaining tilapia, or a chemical treatment to kill off those remaining in the wet bottom.  Neither option is efficient, and chemical treatment is simply undesirable. A raceway provides a much more controlled format for fish removal, from the top and sides, without the deluge.

Additionally, control of fish population has another aspect as well.  Tilapia mature sexually at a very early age.  Females can begin egg production as small as five inches in length, far below eating size.  Unfortunately, the beginning of sexuality in females marks a strong slowing of growth in size.  Thus, once females have mated, they are all but runts as far as profitable production goes.  Certainly they will eventually grow out, but this process will take four and five times longer than in a male.  Thus, in raceways, it is common to introduce only males, separating out the females before they enter the closed system.  This can be done in one of three ways.  First, hand-sexing is the most traditional and most time-consuming of the three.  Each fish must be individually handled and inspected before being placed in the raceway.  A female can be identified by a half moon shaped opening between the anus hole and the urine hole.  The male does not have this extra opening.  It takes a trained eye and a large enough fish to sex out the females quickly to keep the fish out of water the least amount of time.  A swabbing of food coloring on the area can help bring out the female qualities, but this is an extra step and an extra cost.  Hand sexing is labor intensive and as such is relegated to countries whose workers are paid little and worked hard. Still, poorly paid veteran hand=sexers can separate hundreds of fish an hour. The second and third ways to ensure a male population in the raceway are to simply buy male tilapia fry.  These males are created in one of two ways: chemically or genetically.  The chemical treatment involves introducing a hormone to the fish when they are very young to induce the population to become all male.  This hormonal treatment is legal, but is not, in my opinion, desirable, as no hormone treatment is fully beyond my suspicion as to its human ingestion without repercussions.  Further, some females who flip with the treatment, flip back during growth.  Nature will out.  However, scientists have found a way to genetically produce offspring which are 99% YY males.  These YY males are super males, without a speck of femininity to them.  The YY male’s characteristic was first discovered in prisons where ultra-violent men raged beyond the pale of any angry convict.  These berserkers where tested and found to be dominated by a YY syndrome.  They were brutes, the alpha male of alpha males, and were often killers without conscience.  You can imagine how aggressive YY tilapia are in their schools.  At high densities, they will fight tirelessly for territory, stressing the entire school.  And God help any female in the system.  YY males are not interested in mating.  They seem to literally loathe sex and feel compelled to simply kill any female they come across.  In fact, in a pond environment, YY males have been known to hunt down every last female in the pond, leaving none alive.  A raceway full of YY males is a lively place, filled with full throated males hungry for the food and hungry to grow.  At optimal conditions, YY males will reach market size within six to seven months in the raceway.  That is as fast a dollar a farmer can make from selling a source of protein.

Early raceways were operated on a flow-through system wherein the water was always moving from one end pumped from a well, river or other natural source and out the other end back into the surrounding waters.  This provided clean water for the fish, but added often unwanted nutrients to the surrounding waters. Additionally, the effluent water carried the potential for fish release into the wild. Tilapia eggs are as small as tomato seeds, and tilapia fry are not much bigger than a human eyelash, so even the thinnest of screening capture systems could not ensure zero release of stock with the outgoing water.  As tilapia are not native to any part of the United States, although some species have become naturalized (a term of bio-resignation in the face of control failure—man, that silly being always out to control), release of the fish is strictly prohibited and licensing is required to allow for inspections to ensure Best Management One carp farm years ago suffered an uncontrolled release and now carp are terrorizing natural species across the United States. Soe fish hunts drive the carp up rivers for relatively ineffective capture and the fish, larger than watermelons, fly from the water in dozens over the prows of the boats battering the occupants continuously and painfully. Practices are in place and followed in the handling and containment of the tilapia.  Keep in mind that exotics, especially invasive exotics with powerful survival skills and top of the chart reproductivity aided by mouth-brooding, are considered rightfully a threat to the local flora and fauna and must be controlled aggressively.  Enter Dr. D, a genius on several levels including science and marketing.  After an aquaculture conference held in Virginia in the 1980’s, Dr. D envisioned a raceway system that was closed, that recirculated the same water, and treated it naturally to remove toxins harmful to the fish.  This system was not only a water saver, but an environment saver as well.

The concept depends upon a pump to draw the water from one end of the raceway to the other, and up into a denitrification tank.  The tank being on a platform above the surface level of the raceway allows the pumped water to be gravity fed back to the far end of the raceway with no significant water loss or additional energy usage. Think of the raceway as an eighty foot long rectangle, four feet high, filled to just above two feet its entire length (with some slight change if a slope is engineered into the bottom to encourage movement of solids along the raceway floor toward the far end where they can be vacuumed out of the system). The water circulates within the system constantly.  Thus the term recirculation. The denitrification tank is filled with material that would allow certain bacteria to grow on its surface.  This bacteria, in God’s perfect plan, breaks down the ammonia and then the toxic bi-product, nitrites, into safe nitrates that are not only harmless to the fish but also a wonderful source of nitrogen energy for plants.  What substance supplies the ideal surface for the miracle bacteria? Plastic. Thus, by cutting up plastic soda bottles, the tank can be filled inexpensively and made ready for use in no time and at little expense. It is, in fact, recycling at its finest.  The plastic is USDA approved and the reuse keeps the trash mountains from filling that much more rapidly.  Every environmental savings is a savings and not a cost.  A totality of small savings, on a wide scale, can have powerful environmental benefits, or cause less environmental damage at the least.

This system works to control toxins as long as the flow is maintained and the plastic is kept clear of the clogging effects of fish detritus.  This clogging requires additional thought as feeding of the fish is a critical element in their rapid growth.  And the more feed fed, the more detritus is produced.  Thus what we call the dead zone.  The concept of a dead zone or still water section is not new.  It has been used in water and sewage treatment for many years.  The theory is that almost any particulate or solid matter floating in water stays suspended in the water generally because of the water’s motion or current.  The dead zone, through the use of partitions and other turbidity disruptors, slows the water movement down enough so that the solid particles in the water bouncing against the designed barriers move at an ever more declining speed, moving more slowly than the water current and losing height in the water to eventually fall to and remain on the bottom.  This way, by the time the recycled water reaches the uptake pipe to be pumped into the bio-reactor tank and recirculated, most of the particulate matter that would foul the denitrification process has fallen out of circulation and the return water cleansed of suspended solids.  The dead zone becomes a collector for the fallen fish detritus, which is then vacuumed out of the raceway and into the nearby detritus pond.  This represents almost the entire loss of system water daily, less than one percent, and is easily replaced by fresh well water in a few minutes of pumping.  The detritus pond itself, rather than being a waste collection unit, becomes a golden pond for growing ornamental fish like black mollies, a hydroponics farm for growing fresh tomatoes and herbs, a source of rich irrigation water for in-ground row crops and trees and flowers, and a producer of some of the most valuable fertilizer on the planet.  We grow papyrus in the pond and then move it to the raceway where it aids in ammonia removal while the fish nibble away at the succulent roots.  The papyrus is a hardy plant and grows rapidly, almost enough to out grow the feeding fish.  When the fish have eaten away all the roots, the stalks are removed, mulched, and new plants are introduced. Further, with the modern awareness of the need to mitigate half a century of wetland destruction, the detritus pond is an ideal wetland plant propagule nursery media. In effect, the dead zone of the raceway becomes a revival zone for transformed materials and nothing is wasted. In fact, as Dr. D has developed it, a series of shallow ponds fed from the raceway filled with wetland propagules such as native mangroves can become an ultimate water revivifier.  The detritus itself serves as a fine planting media in which to set the wetland propagules in nursery pots.  Once the propagules are potted, they simply sit in the detritus ponds and thrive on the nutrient-rich water. As water trickles from detritus pond to detritus pond, the propagules use the ammonia and nitrates in their growth.  The dissolved solids, trickling along with the water, tumbling against the nursery pots and pond walls, gently settle to the pond floor.  At the far end of the last pond, a small motor pumps the water back into the fish raceway.  That water has been clarified of solids and denitrified naturally by the plants.  The system becomes practically 100% self-sustaining.  Only evaporation in this system needs to be replaced and this natural process of course varies with surface exposure of water, wind speed and fetch, and air temperature. If the only element of water loss is evaporation, the farm has approached a perfect environmental system.  It uses nature to purify the water for reuse and sacrifices a little evaporation.  Within the closed hoop house, the evaporation appears like incense rising up in some mystic ritual in praise of God’s occult genius and His bestowal of an aching curiosity and process of logic and trial and error which comprise mankind’s only potential for social and personal advancement.  The water will evaporate, though even that can be reduced with a capture method. The entire process deserves a “hallelujah” of psalm and praise to the Great Designer.

One caveat must be addressed with slow-moving water such as found in the detritus pond system: mosquitoes.  Mosquito larvae cannot swim but rather only wriggle to the surface and back down a few inches in their larval state.  Thus, mosquito larvae do not do well in running water such a streams and rivers.  But still water and slow-moving water can be ideal for larval growth.  In fact, even some air plants, such as bromeliads,

which are designed to collect rainwater at the wide base of their leaves may become mosquito nurseries during the warm and rainy season. In the detritus pond, this threat  can be addressed with fish, not tilapia, but ornamentals.  Small aquarium fish, such as mollies and fancy guppies do very well in the slightly saline water and will be happy to feed on the protein rich mosquito larva.  They will gobble up frog tadpoles as well and live strong and produce many young.  These ornamentals, after they have multiplied sufficiently, can become a supplemental source of farm income once removed from the ponds, treated for ick and other natural diseases which no aquarium aficionado wants introduced into her home tank, bagged and sold to local pet stores or flea markets. In this way, once again, a need in the system can be addresses with a natural solution which in itself becomes a cottage industry.

Another experimental advancement which aids the bioreactor tank in the denitrification process is the biowheel.  Our biowheel might be created from an empty plastic fifty five gallon drum. Sections of aluminum gutter cut the length of the drum are screwed into the drum’s sides in five equal sections using stainless steel screws to prevent rust deterioration. These serve somewhat as paddle wheels. The entire drum is wrapped in heavy plastic netting creating pockets from gutter to gutter.  These pockets are filled with plastic which will become the media for denitrifying bacteria growth (held on the wheel by the netting).  The drum’s top and bottom become its sides when laid horizontally and are cut through so that a four inch pvc pipe can be inserted and run through and out like an axle.  This pvc pipe extends all the way across the raceway as much as ten feet from side to side and rests on the upper raceway rail.  The gravity fed water returning from the bioreactor is piped across the raceway a few feet from the biowheel.  Half inch holes drilled into this return pipe direct a water spray from the return pressure up into the air (oxygenating the water) and against the side of the biowheel, splashing through the mesh sides, onto the plastic (thus further denitrifying the water and further oxygenating the water) to fill the gutters.  As the gutter fills, the weight on that side of the biowheel increases and the wheel turns to spill out the collected water.  With the turn, the next gutter is exposed to the return water and it fills and weighs down and turns.  In this way, the biowheel is in constant motion, turning simply through the energy of the gravity fed water.  The advantage of the turning wheel is that no solids can collect on the plastic and foul the denitrification process.  It is a self-cleaning system which requires no energy to run, something of a mega version found in some home aquarium filters.

So, the raceway, a closed recirculating system which uses a minimum of water, and re-uses even that water, produces fish efficiently, and provides fertilizer for crops and mangroves, an environment for ornamental fish, and sustains itself on a small amount of electricity. The theory of the closed system is similar to that of an aquarium in your living room, without the need for charcoal and cloth filters which clog rapidly. So, the theory works from very small to very large.  This means that anyone with interest can set up a system to suit her whims, raising her own tilapia for the family in a backyard above-ground pool for example, while growing the lettuce and tomatoes for the night’s dinner salad from the water in which the fish are growing.  What safer food source can you have than food grown yourself?