The Best Of Both Worlds
Aquaponics combines aquaculture with hydroponics. Here is asimple, step-by-step approach to setting up and maintaining your own small but productive aquaponic garden
This article will cover the basics of hobby aquaponics, and give step by step instructions on how to build and maintain a small flood and drain aquaponics system.
What is aquaponics?
Aquaponics is the combination of recalculating aquaculture (fish farming) and hydroponics (growing plants without soil). The fish waste provides the nutrients the plants need and the plants, in taking up these nutrients, help to purify the water in which the fish live. This is an organic process with the only input to the system being fish food, which creates a sustainable ecosystem where both plants and fish can thrive.
Aquaponics is particularly successful for growing leafy crops such as lettuce, herbs, chives, spinach, arugula etc. because of the high nitrogen content in the water. Other food crops do well, including tomatoes, cucumbers, peppers, beans, peas, squash andmelons, but these fruiting plants may not produce as high a yield as with hydroponics-only systems, where higher levels of phosphorous and potassium can be maintained.
What about the fish?
Tilapia are generally the fish of choice for larger aquaponic systems because they are fast growing, can tolerate a wide variety of water quality conditions and have firm white meat. For small hobby systems koi or gold fish work well.
It is a good idea to also include a plecostomus cat to help keep the tank clean.
Start with approximately one inch of fish for each gallon of water in the tank.
Materials for the system
• Tank – Virtually any clean container that can hold ten or more gallons of water will work, but for esthetics and function, fish aquariums work best for most small systems. Fortunately these are readily available used.
• Under gravel filter and pump – These can be built but it is easier to buy them and generally they come with used tanks. The filter needs a means of pulling water through the gravel to promote bio-filtration. This can either be done with an air pump and air stones, or with devices known as "power heads," which have an active water pump that draws water up the riser tubes of the filter. The best setup is to have the power heads for the filter and then supplement the dissolved oxygen in the tank with an air pump and air stones. Air hose tubing will be needed as well as a two way gang valve.
• Grow bed – The grow bed can be any container that can sit on top of the tank and that can have holes easily drilled in the bottom. Dish pans or plastic storage bins work well for this and can be found at discount stores. The objective is to find something five to seven inches deep that covers most of the tank surface, but is wide enough to sit on top. Leave a small space for feeding the fish. For ease in maintenance, two or three smaller containers can be placed side by side on top of the tank.
• Submersible pump – A pump is needed to flood the grow bed. For systems of up to two square feed of growing surface, a 160 GPH submersible hydroponics pump should be sufficient.
• Tubing – Sufficient tubing is needed to go from the pump at the bottom of the tank to the grow bed and to cross the length of the grow bed twice.
• Aquarium gravel – Don't skimp on this. Other gravels may be less expensive, but they will leach into your water and impact the ph. Buy actual aquarium gravel, enough to cover the under-gravel filter with two inches.
• Growing medium – For this system expanded clay pebbles work well. These are sold under several brand names and can be purchased from any retail hydroponics dealer. Enough will be needed to fill the grow beds to within one inch of the top.
• pH Test Kit – This system is very easy to maintain, but starting with proper pH and maintaining it is the key to success. Test kits are available for as little as $5 at hardware and pool stores.
• Siphon cleaner – This inexpensive tool is available at all stores that sell aquariums and is indispensable for monthly tank maintenance.
• Hydroponics nutrient (optional) – The nice thing about an aquaponics system is that the system will produce ample nitrogen needed for green leafy plants to thrive. It is not necessary, but to help maintain better phosphorous, potassium and micro-nutrient levels add a quarter of the recommended amount of a good hydroponics bloom formula to the replacement water.
• Light source – If the tank is placed near a sunny window additional light might not be needed. This may not be adequate if the system is relying entirely on artificial light. 20-50 watts per square foot is a good rule of thumb for grow lights if used exclusively. A small stand can easily be made of PCV pipe to hang the light fixture from.
Setting up the system
The tank will be set up just like any aquarium. Place the under-gravel filter in the tank with the riser tubes installed, add gravel and then water. Connect air stones to tubing from the air pump and insert them into the riser tubes from the filter or insert and plug in power heads. Once water has been added to the tank, check the pH and adjust as needed. If the system was just for raising fish it would be best to try to maintain the water at a pH of about 7.4. In aquaponics the needs of both the plants and fish must be slightly compromised by maintaining a pH of about 6.8. More often than not the pH of tap water needs to be lowered. Products for raising and lowering pH that are safe for both plants and fish are available at both hydroponics and fish stores.
If fish are to be added immediately the water must be de-chlorinated, otherwise wait 48 hours before adding the fish. To start your system, add approximately one inch of fish for each gallon of water.
The grow bed will need one hole in the bottom large enough to feed the pump tubing up through and 3/16th inch drain holes every two inches. As the grow bed will be slightly larger than the tank, make sure not to have drain holes near the edges. Most submersible hydroponics pumps come with suction cups that can be used to install the pump on the side of the tank near the bottom. If the pump does not have them it will be necessary to lay a flat slate, or rock on the bottom to set the pump on so it will not clog with gravel. Use a small drill bit to drill holes in both sides of the feed tube in all but the section that will go from the pump up to the grow bed. Feed the tube up through the hole in the grow bed and loop the rest of the line down one side and back up the other of the grow bed. Fold the tube over twice and secure with a zip tie or strong rubber band to block the end of the tube and force the flow out the holes in either side of the tube. If more than one grow bed is used, cut a small notch or hole in the top of the beds for the tube to fit through. Fill the bed with expanded clay medium, or other suitable growing medium, to within one inch from the top and place the feed hose on top. If necessary, to avoid splashing it is helpful to place a small amount of medium on top of the feed hose.
Let the system become established for one month with the fish before adding plants. Plants can be started from seeds directly in the grow beds or they can be started in peat and transplanted to the grow beds.
Maintenance
The good news is that this system is easy to maintain. Check the pH weekly, if it's between 6.6 and 7.0 things are going well. If the pH is outside this range, adjust itby using either pH Up or Down as needed. A pH of 6.8 is ideal. Top off the tank with de-chlorinated water that has been supplemented to make a quarter strength hydroponics bloom solution. Each month, use a siphon cleaner to vacuum the excess waste out of the gravel. Take the tank water level down a quarter with this process. Don't throw this water down the drain; it will do wonders for indoor and outdoor plants. Fill the tank back up to the top with de-chlorinated quarter strength hydroponics bloom formula.
This small system can not only be an attractive conversation piece, it also can provide enough salad greens and herbs for the whole family.
