The Outdoor Activity Center Needs a New Water Feature!

This fall we hope to build an aquaponic garden at the Outdoor Activity Center. We are expanding our frog pond, adding a water feature for education and aesthetics. We were connected with Dr David Epstein who developed an integrated system for his home and is marketing this system as a new totally sustainable way to garden and produce food!

He built his system for raising tilapia and growing vegetables and describes his system as an ecosystem model, mimicking bogs or bays, supporting life on many levels.  Aquaponic utilizes fish and their waste produced as the nutrient source for growing plants. Plant beds and the naturally developing biofilm of microorganisms convert the ammonia to nitrogen, which provides nutrients for the plants and removes the toxic ammonia from the water, as a biological filter for the fish. What excites him and is encouraging for us as environmental educators is that visitors can not only watch as fish, herbs and vegetables are produced, but they can also witness the interaction played out in the many ecosystems that are simulated  in the aquaponic garden that some might never see close at hand.

According to Dr Epstein most backyard aquaponics are ebb and flow designs. As such, water from the fish tank floods a soil-less rock bed and drains back to the tank throughout the day. His system floods and drains every hour for 15 minutes.  Ebb and flow is nice for several reasons: the rock medium supports a large root system, it requires little energy to run a low volume pump on a periodic basis, they are easy to work with when sowing seeds, transplanting or by starting clippings and the rocks also filter out the solid matter from the water. In addition, ebb and flow bed rocks make an ideal substrate for bacteria to naturally colonize and complete the nitrogen cycle. One major reason that ebb and flow is host to the friendly aerobic bacteria is that by flooding and draining, the oxygen is drawn in and exhausted air expired from the system with each flood and drain. 

David has also experimented with deep water culture designs, which is more often used in hydroponics. With this, water is continuously moving under floating rafts that allow the plant roots to spread freely, trapping and filtering nutrient rich water as it passes through.  He describes the many symbiotic relationships he encounters from his home system, "generally, deep water culture within aquaponics does not include all the elements I have experimented with. They are often adjusted to maximum yield by using clarifiers, degassers and other devices to remove fish solids. But I have found that allowing the waste to remain and by introducing other natural bog elements more ecosystems are created, adding biodiversity to the entire garden.  There are damselflies that morph from the water in the early morning. The nymphs or naiads crawl from the water during the night and become flying damsels as they shed their skin, leaving behind only the form of their transitional bodies along the walls of the bed. They hover about, dancing in the air, in a joyful display of affection for their environment.

Damselfly nymphs in the water play their own roles in this ecosystem, living on leaves of aquatic plants, they feeding off of baby fish and aquatic insects. Their predators include larger aquatic insects and fish. Damselflies themselves are considered beneficial insects as they prey on fruit flies, mosquitoes and gnats. And considering all the rain we’ve had this summer, their presence brings pleasant thoughts.  Another remarkable discovery is that honey bees now land on the floating duckweed that is growing in the water beds. They come one by one and two by two, every 10 or 15 seconds, from morning till early evening. Evidently the bog flavored water suits them well as they have found it a regular watering hole, to which they are very favorable. Certainly this is an ecosystem that can be easily appreciated at a time when honey bees welfare is otherwise threatened. They are a reassuring sight in any fruit bearing garden.  Anacharis is an aquatic plant that I have introduced to the water beds. After the tilapia eggs hatched and the fish fry appeared, I noticed they spend time hiding out among these plants. Evidently this is not only for protection from predators, but also they are feeding on the plankton, or protozoan, that populates the same area. As it goes, anacharis, which stays completely immersed in water, produces oxygen on its leaves during photosynthesis. Underwater oxygen supports aerobic bacteria, which in turn feeds the plankton. These protozoans are a primary food for the baby fish. This ecosystem is one that is proving to be valuable, as raising fish fry can be a delicate process. Without any effort, the bog environment provides for itself, making an ideal habitat for raising fish. I have added crawfish for their role in producing phosphorus, a nutrient that aids in the flowering of aquaponic plants and soon, frogs, which will eat insects and provide another cycle of life with their eggs and tadpoles.  What I have learned about nature while raising vegetables and fish in my aquaponic ecosystem, has given me back my youth. When I am in the garden, I feel like a child, re-discovering the nuances of life, as it unfolds in a most delightful way."

Once we have installed the garden we will develop an activity guide that school groups and other visitors can use to scientifically monitor changes in the fish and plants produced and record their observations.

If any one has heard of these types of systems and wants to comment, is interested in volunteering to help install our system or wants to contribute resources for our project please respond!

Dr Dave Earth SolutionsTo contact Dr Dave Epstein try these links: