Aquaponics is the combined culture of fish and plants in recirculating systems. Nutrients, which are excreted directly by the fish or generated by the microbial breakdown of organic wastes, are absorbed by plants cultured hydroponically (without soil). Fish feed provides most of the nutrients required for plant growth. As the aquaculture effluent flows through the hydroponic component of the recirculating system, fish waste metabolites are removed by nitrification and direct uptake by the plants, thereby treating the water, which flows back to the fish-rearing component for reuse. In my system tilapia will be produced along with a variety of herbs, leafy plants, vegetables, and perhaps fruits.
The aquaponic system I will be utilizing is a scaled down version of the University of the Virgin Islands commercial scale system. It is roughly 1/8th the size of the UVI system, but may be multiplied in accordance with resources and demand.
The UVI system has been producing tilapia for more than a decade. It is a proven system and detailed information relating to it is freely available, including some of this text which I am, honestly, guilty of plagiarizing freely at times. Thank you Dr. Rakocy. I wish I could afford to go to the Virgin Islands and take part in one of your training programs, but I’ve got to do it the hard way.
Aquaponics has several advantages over other recirculating aquaculture systems and hydroponic systems that use inorganic nutrients solutions. The hydroponic component serves as a bio-filter, and therefore a separate bio-filter is not needed as in other recirculating systems. Aquaponic systems have the only bio-filter that generates income, which is obtained from the sale of hydroponic produce such as vegetables, herbs, and flowers. In the UVI system, which I copy, and which utilizes employs raft hydroponics, only calcium, potassium and iron are supplemented. The nutrients provided by the fish would normally be discharged and could contribute to pollution. Removal of nutrients by plants prolongs water use and minimizes discharge. Aquaponic systems require less water quality monitoring than individual recirculating systems for fish or hydroponic plant production. Aquaponics increases profit potential due to free nutrients for plants, lower water requirements, elimination of a separate bio-filter, less water quality monitoring and shared costs for operation and infrastructure.
The aquaponic system I envision is perhaps somewhat unique for several reasons, but it is still based on a functional, replicable, system that has been proven to be not necessarily the most productive, but advantageous for several reasons.
- Due to a larger water volume using the raft hydroponic system (compared to other aquaponic system models), fish may be raised without plants. In other words, there will be enough water to raise the fish without the plants, in case I kill all the plants by accident or never coax them into existence in the first place. This has something to do with having enough surface area to allow the good bacteria to do their thing (using layman’s terms) with the nasty stuff that the fish produce.
- My aquaponic system will be directly attached to a mushroom cultivation “bunker” built into a hillside, much like root cellar. Mushrooms produce huge amounts of CO2, which at times, depending on the needs of the mushrooms, needs to be expelled. It can be easilly channeled into the aquaponic greenhouse. Increases in CO2 have been proven to improve plant growth.
The combined mushroom bunker/aquaponics greenhouse idea was merely an attempt to simplify construction (originally I intended separate buildings). It makes sense to share walls when you can, especially when building with earthbags, as the walls are thicker to begin with. I don’t remember how I stumbled onto the fact that commercial greenhouse growers often go to extremes to infuse their greenhouses with extra CO2. Mushrooms, somewhere, was posited as having great potential to this effect. As a mate of mine pointed out, Google sucks unless you ask it the right questions. But I’m far from confirming the theory, as I’ve still got to coax the little buggers (plants, I mean) into existence in the first place.
The most recent design looks something like this. It has gone through more revisions than you can imagine. It is now designed so that it can be built in three independent sections, but that’s a construction matter that doesn’t pertain to aquaponics. I’ll show you how I intend to build it elsewhere.
Differences between the UVI system and mine are that I’ll try to produce 33% more fish with less overall volume of water. The UVI system tries to eliminate the manipulation of fish because it makes them unhappy. So, you put little tiny fish into a big tank and they stay there until they are big and tasty looking and then you filet them and start the process over again. But since my basic, single aquaponic component comprises only 2 fish rearing tanks instead of the four in the UVI model, using hapas, which are basically cages made of fine mesh, will enable me to keep the little tiny fish with the not-so-big fish at the same time in the same tank. After the big, tasty looking fish in the other tank are sent to their demise, the little fellows will be moved to where the big fellows were. The not-so-big fellows in the tank that the little fellows just left from become the next big fellows. I hope this isn’t too technical.
Excluding the 33% increase in fish production that I envision, which I can’t claim is possible as I haven’t done it, the following approximate figures are not just fanciful witch-craft numbers.
- Total fish tank water volume, 4 cubic meters
- Hydroponic tank surface area, 22.5 square meters
- Total annual tilapia production, 700kg
- Annual plant production (lettuce) 5,280 plants (192 plants per square meter)
- Annual plant production (basil) 644kg (23.4kg per square meter)
- Annual plant production (water spinach) 4,263kg (155kg per square meter)
The ability of water spinach to reproduce and grow is extraordinary. It is also convenient that it is very popular in this part of the world. It is even more convenient that the leaves of the plant are extremely high in protein.
For the sake of argument, let’s take the fish production at at face value and average the vegetable production. So, we still get 700kg of fish a year, and let’s say, 2,500kg or so of vegetables. So that’s about 3.2 tons of what we shall presume is a healthy diet.
I thought this could feed a small village but, according to what I’ve researched, it a can only provide enough nutrition for two fat Americans.
The average American consumes about 2,175 pounds of food per person per year, which provide about 3,600 Calories of food energy per day. This daily intake contrasts with the worldwide average of 2,700 Calories.