Thursday, May 31, 2012
Carponics [kahr-pon-iks] n. The process of nourishing plants with effluent from ornamental carp.
Okay, I just made up the word carponics, but it describes in a word the process I use to feed my plants and keep aesthetically-pleasing fish in my deck garden. “Ponics” in Latin means “working”, as in hydroponics or aquaponics (“hydro” and “aqua” both translate to “water”). Carp is the species to which goldfish and Koi belong. These types of fish are working to provide fertilizer for my plants (if you call excreting waste “work”), so I named the process carponics.
In my garden, I use a very low-tech system, but for innovative gardeners with an extensive garden (or little time for irrigation), an automated system with a timer could be used.
Fish Tank Set-up
Three years ago, I bought a 32-gallon plastic bin (food-grade plastic is recommended) as a makeshift fish tank and it has held up very well outside under shelter. It does tend to bow out, so I fill it only 2/3 full of water and put it between other heavy bins to help hold its shape. You can find the rest of the items for the tank at a pet store. You will need de-chlorinator drops, an air pump, tubing, a bubble stone, goldfish food flakes, 8-10 feeder goldfish or Koi, and a heater for winter months. You may also want to purchase an ammonia filter and tester if the water will not be changed often. I also added a couple of fish caves for extra shade and a Blue Mystery snail to keep the algae under control. My teenage daughter has several aquariums so we had many of these items on hand. I did not use gravel because fish waste would settle in it, reducing the amount of fertilizer available for plants. If you are a hobby aquarist and have a pH monitor and thermometer on hand, these would also be beneficial. I tried using aquatic plants for more cover, but the goldfish quickly devoured every bit of the plants.
My first fish were so hardy that they survived a winter outside (with an aquarium heater) and a move across two states in a cooler in our vehicle. They were fed well (but not overfed) and they grew quickly, especially with the frequent water changes. They did well in their new spot outside on a ground-level covered patio next to some woods…what they didn’t survive was the sly fox that came for dinner one night. If you are in an area where wildlife may appear, I would suggest keeping a screen over the tank at night or keeping the tank on an elevated porch or deck where animals would be less likely to visit. We have started over with new feeder fish this season and they seem to be thriving.
Because a large portion of this blog is dedicated to gardening in self-watering containers, I feel that I should mention that I do not use fish effluent in our self-watering bins. With these containers, I prefer using the small amount of chlorine in our city water to help prevent undesirable bacteria from growing. I don’t know of any scientific studies on this, but my intuition tells me that one should not add fish effluent to a dark, enclosed space with standing water to be wicked up to vegetable roots. I do have evidence (the health of my family and garden) that adding the effluent to soil in pots with good drainage is beneficial as a mild fertilizer.
For more information on carponics and how it differs from aquaponics, as well a description of watering methods I use, and reasons that fish effluent is good for plants, please visit an informative blog called Suburban Hobby Farmer . It is hosted by Bill Brikiatis who is an excellent garden writer on growing food organically in your backyard. I guest-authored a companion post to this article this week.
Thanks so much for reading, and blessings on your gardens!