Our systems

Our first system, built from food grade stock troughs

This is our first system.  The top bed is 70 gallons and the bottom bed is 100 gallons.  It is constructed of food grade stock troughs.  It is a fill and drain system.  We have since constructed two smaller and much less expensive systems.  The bottom tanks are only 30 gallons and the top tanks are only 15 gallons.  These two systems are also fill and drain systems, but we used Sterilite tupperware containers instead of stock troughs.  According to the official Sterilite website, Sterilite products are constructed of food grade plastics.  The other major change in our second and third systems is the switch from the expensive hydroton to the much less expensive and much easier to find lava rock.  Lava rock also weighs a little less.  It requires a lot more rinsing initially, but the plants seem to love it.

We set up our first system for about 450 dollars.  Our second and third systems which are identical to each other ran 125 dollars each.  Since they are in our greenhouse and receive excellent sun year round, they actually produce more vegetables than the larger system.  We do not keep full grown tilapia in the two smaller systems.  Those systems are for small fingerlings, or any other smaller fish.

We originally set up our first system with koi from Petsmart because we has so many problems finding tilapia fingerlings locally for purchase.  One of the truly helpful folks at White Brook Tilapia suggested goldfish.  Feeder goldfish are cheap.  We chose koi because we didn’t know what we’d do with 100 or so feeder goldfish when we were done with them.  Of course, now we have three koi that are a few years old and getting bigger…

We found the stock tanks for the first system locally at Orange County Farm Supply.  They are food grade plastic.  Not all stock tanks are food grade plastic.  The fish tank is 100 gallons and measures 4 feet by 2 feet by 2 feet deep.  It fits nicely into our space and it is a good size for a fish tank.  The grow bed is 70 gallons and measures 6 feet by 2 feet by 1 foot deep.  The grow bed reaches over the entire fish tank, shading it, protecting it from predators, and preventing the jumping tilapia from leaping to their doom.  The fish tank is offset from the grow bed so that we have access to the tank.  More access would have been better.  The grow bed rests on cinder blocks and redwood planks.  We used a level to make sure the grow bed sat evenly.  It looks radically uneven to the casual observer; the northern end of the space is apparently much lower than the southern end.

Tilapia are warm water fish.  Koi are cold water fish.  Don’t mix the two like we did. We do not breed these tilapia so we try to maintain the water at approximately 70 degrees.  Not too hot for the koi and not too cold for the tilapia.  In the summer, we turn off the water heaters.  During the winter, we run two 90 gallon heaters to maintain the water.  We use a large pond pump to move the water from the fish tank into the grow bed via a pond hose.  The hose is clamped to the grow bed.  The two systems in the greenhouse contain only tilapia.  These systems are maintained at 76 to 80 degrees and help to heat the greenhouse in the ‘winter’.

Originally, we had a 15-minute timer that turned the pump on and off every fifteen minutes.  That kills the pumps. So, once we had the tanks stabilized, we just let the pumps run. The bed fills, waters the plants, and then, drains back to the fish tank.  As water is always flowing into the fish tank, it is rare that the level in the fish tank drops significantly.  Six holes are drilled (7/32″ size drill bit) in the middle of the grow bed for drainage.  This is a little too much drainage so we use washers stuck in the holes to change the flow.  The pump is also adjustable.  The desired amount of water in the grow bed at the end of a cycle is about one inch below the surface of the hydroton.  Debris from the hydroton occasionally blocks the holes.  I use a fire engine red chopstick to clear the holes from time to time.  This is not the most high tech operation in existence.

We top the water in the system when needed with our garden hose which has a charcoal filter designed for use on an RV.  The Camco 40043 TastePURE RV water Filter with a flexible hose protector was purchased from Amazon for approximately 18 dollars.  The hose filter enables us to fill the fish tank with water that has been dechlorinated, quickly.

Once the fish were in the tank and we had seedlings sprouting, we added red wriggler worms to the system.  They assist in breaking down the fish waste for the plants and in setting up the natural biological filter that develops in the system once its settled.

Final cost, 449 dollars.

Grow bed, 90.00 at Orange County Farm Supply

Fish tank, 110.00 at Orange County Farm Supply

Sunterra 114516 Medium Fountain Pump, 130 GPH, 15.00, Amazon.  We later switched to the Large Fountain Pump.

ESU Coralife Digital Thermometer item #232, 8.00, Amazon.  After 2 years and several drops into the tank, we needed a new one.

Aqueaon Submersible Aquarium Heater, 300W, 90 gallon heater, 21.00, Amazon One lone heater did not cut it once ‘winter’ started.  We needed a second one.  Also, do not place the heater onto the side of the plastic tank when on.  It won’t work out well.  I promise.

5 bags of hydroton,  150.00, Green Coast Hydroponics

mason blocks, redwood planks, tubing for pump, 40.00, Home Depot

Oracle Garden Supply 24 hour timer, 15.00, Green Coast Hydroponics

While working on the set up of this system, we noticed that Home Depot carries a small ready made aquaponics system online.  This system has space for a small 10 gallon fish tank and it has a small grow bed.  The Little Tokyo Farm in a Box sells for just under 300 dollars and includes everything needed except the 10 gallon fish tank.  PetCo has a small 3 gallon system they sell for 70 dollars.  It contains everything you need to grow a few herbs.

This is one of the smaller systems.  We’ve placed screening inside the original lid for the large Sterilite tub so there can be no jumping out of the tank.  These two systems sit on a wooden frame inside the greenhouse.  For our next system, we want to set up an ebb and flow system that uses a siphon.  Our neighbor has an old tank she inherited that she’s offered to us. The price is perfect.


What medium to use?