Mar 07, 2014 10:04AM
By Readerle Clay
What is Aquaponics?
Aquaponics is a combination of fish farming (aquaculture) and soilless gardening (hydroponics). The nitrate-rich fish waste produced by fish in the fish tank fertilize plants in the grow bed; the plants act as filters and return clean water to the fish. (For more information, see the article “Food Revolution in a Tank: Aquaponics Offers Year-Round Homegrown Fish and Veggies” in March’s edition of Natural Awakenings.)
The components of an aquaponics system are straightforward: a fish tank with fish, a water pump, a grow bed with medium, and a siphon. The pump feeds water to the grow bed and the siphon drains water back into the fish tank.
Purchase a system online or at an aquaponics store, but expect to spend over $600 (source: www.theaquaponicstore.com) or even as much as $2,000 (www.aquaponicsusa.com) for a complete kit. The unit can be built at home for $175 or less.
Grow bed media
Building an aquaponics system at home can be accomplished with a trip to a hardware store and, optionally, a trip to a pet store.
- HDX 36”W x 16”L x 72”H ($70)
- HDX 4” swivel casters (optional, $20)
- Rubbermaid Roughneck 14gal. tote ($7.30)
- ¾” OD – 5/8” ID 10’ vinyl tubing ($8)
- JB Water Weld adhesive ($6)
- Washing machine stainless steel mesh lint trap ($2)
- Landscaping lava rock (4 bags, $14)
- 7/8 x 4 x 8 cedar lumber, cut in half ($10)
- Philips 75w plant light bulbs and 5.5” clamping fixtures (2, optional, $28 ea.)
- Defiant Heavy Duty automatic timers (2, optional, $30)
Plan to use a 30 gallon fish tank and a canister filter (I use a Marineland Magnum 330). Which can be bought from a pet store or they can be found used. The tubing and fittings for the canister filter should be no larger than 5/8” inside diameter (ID); if the tubing is larger, increase the size of the vinyl tubing (on shopping list above) to one size larger ID than the ID of the tubing for the canister filter.
First step in the assembly is to put the shelving unit together. The casters (wheels) are recommended to make it easier to move the unit once the tank and grow bed are in place and filled. Follow assembly instructions for the shelving unit and casters.
The first shelf should be placed near the bottom; this will host the canister filter/pump. Use a tape measure to determine how high the second shelf should be placed in order to provide clearance for the pump. Make sure to account for the tubing coming out of the top of the pump and running to the fish tank and the grow bed. (Alternatively, you can use a board, secured to the bottom shelf to hold the pump and place the subsequent shelves lower.) Use a tape measure to place the third shelf above the fish tank, providing an additional 4-6” of clearance for the tank hood. The grow bed will rest on the third shelf. Optionally, a fourth shelf can be placed at the very top of the shelving unit to provide a trellis-type anchor for plants as well as an anchor for plant lights (if using).
Measure 2-3” from the top of the tote and drill or cut a ¾” hole through the end below the tote’s handle. Thread the vinyl tubing through until the inner end is approximately 2” from the bottom of the tote. Place the lint trap over the inner end of the tubing to prevent grow bed medium from entering the tubing.
Place the empty tote (grow bed) on the third shelf. Place two of the cedar boards on either side along the length of the shelving unit, bracing the ends on the posts of the shelves. The tote will flex once the lava rock is added and will cause the siphon to fail; the boards provide the extra support needed to prevent flexing. Add enough of the lava rock to hold the inner end of the vinyl tubing securely in place. It is highly recommended that the lava rock be thoroughly rinsed before being put in the grow bed.
Measure out the amount of tubing needed to drain safely back into the fish tank and trim the tubing to the appropriate length; you should need between 3 and 4 feet. The tubing should go over the top of the support boards in order to provide some back pressure. Once the grow bed and tubing are in place, seal the tubing in place on the inside and outside of the grow bed using the JB Water Weld (follow package directions and all safety precaution when using JB Weld). Allow time for the JB Weld to cure.
While the JB Weld cures, place the fish tank on the second shelf and fill with water. The canister filter needs to be set up to pull water from the bottom of one end of the fish tank and to pump water into the end of the grow bed opposite the siphon tubing. The siphon will drain into the end of the fish tank opposite of the canister pump’s intake line in order to cycle water completely through the system. No filtering media or filter should be placed in the canister filter, its only responsibility is to pump water (not filter the water).
After the JB Weld is cured (approximately 3 hours), fill the grow bed with lava rock and turn the pump on. Monitor the system carefully, but when the water reaches approximately 2” from the top of the grow bed, the siphon should seal and water will drain out of the grow bed and back into the fish tank.
Let the system run for at least a week to ensure that any remaining grit from the lava rock settles out and to troubleshoot any problems with the pump and siphon. Once the system has run for a week with no manual interference to ensure that it remains running properly, you can add fish. Initially, small goldfish are recommended in case any issues with the system arise; these fish are typically priced at 10-15 cents apiece and provide sufficient nutrients for plants. Food fish can be added later as the fish tank environment stabilizes. The fish should live in the tank for 3-4 weeks before adding plants to the grow bed to allow the ammonia-nitrite-nitrate bacteria cycle to become firmly established and provide nutrients to the plants.
Your aquaponics system is now established and you will be reaping the benefits before you know it!
The system described above is capable of supporting fruiting plants such as tomatoes and cucumbers; shallower grow beds (less than 12” deep) will not provide the root support required for fruiting varieties. Heirloom vine varieties are recommended: they’re more flavorful, the vines will convert easily to additional roots as the plant grows, and the plants can be trained to a trellis system.
The rule-of-thumb for the size of the fish tank versus the size of the grow bed is roughly 1:1 water to grow bed medium. 0.6:1 and 2:1 are common ratios, as well, where the 2:1 ratio of water to medium is better for fruiting plants (more water can sustain more fish, which in turn provide more nutrients for the plants).
To determine the number of fish you need, in a 1:1 ratio setup, one 1-inch fish per gallon of water will provide sufficient nutrients for non-fruiting plants. With basic goldfish (which grow up to 4-8” long), this works out to about 10-15 fish in the setup described above (30 gallon tank to 14 gallons of lava rock). Start with the smaller fish and allow them to grow along with your plants; as they get larger and output more waste, your plants will mature and require additional nutrients.