AQUAponics versus HYDROponics
- There has been a lot of food-related new stories surfacing recently. The FDA just expressed their growing concern over the dramatic increase in antibiotics in our food supply. Additionally, a long term study was just released stating that vitamin supplements have no benefits to our health. Due to this and other issues gaining popularity in mainstream media, more and more Americans are beginning to explore growing their own food. Many people seem to confuse Aquaponics with Hydroponics. The two are very different, so I thought it would make sense to outline some of the differences to clarify for the readers who may be thinking about growing their own fresh fruits and vegetables in an effort to increase longevity.
Relationship with bacteria
Hydroponic systems tend to be fairly sterile. Many hydroponic growing facilities require you to wear coveralls and a hairnet to enter. Not so with aquaponics. Bacteria are revered by aquaponic gardeners because they are the engine that drives the systems. New systems tend to require a little more work to maintain (still less than a soil-based garden), but once your system matures, the magic really takes over. The bacteria becomes the engine for amazing growth and production.
Fill and Drain cycles
Hydroponic growers using flood and drain techniques generally only fertigate their plants once every four to six hours. Academic studies and collective experience have shown that this optimizes the water and fertilizer the plants need. When you move to an aquaponics system however, the ideal schedule changes to flooding for 15 minutes every 45 minutes. The reason is that the grow bed now has taken on the additional role of being the filter for the fish waste. If you only ran the fish water through the filter every four to six hours, fish waste would build to dangerous levels.
Depth of Grow Beds
Hydroponic growers tend to use standard 6 inch deep flood tables and put pots or cubes with plants in them. With aquaponics, the grow bed is serving a dual role of both home for the plants and bio-filter for the fish waste, both need to be considered and optimized. Most media based aquaponic gardeners use 12 inch deep grow beds filled with an inert media. Over the years, side by side trials have shown that this depth of grow bed develops the kind of robust bacteria colony needed to not only filter the liquid waste, but also to provide an excellent home for composting red worms and the heterotrophic bacteria needed to break down the solid waste from the fish.
Hydroponic gardeners live and die by their nutrients, and the supplements to those nutrients. Not so with aquaponic gardeners. The goal of an aquaponic garden is to achieve a “state of balance” within its ecosystem. Everything that goes into the system must work towards this end goal, and not harm any other element of the system. Anything added to the system to boost plant growth could, harm the fish and possibly the bacteria colony and the compost worms. There are a few exceptions to this, including the use of a liquid seaweed and small amounts of chelated iron, and a few minerals to adjust pH. Beyond these, aquaponic gardeners will think long and hard before adding anything to their systems except of course, fish feed. The benefir of course is that the food grown will be 100% organic & natural.
Hydroponic nutrients must be dumped and replaced on a regular basis to address nutrient imbalances that arise over time. This concept mystifies an aquaponic gardener. We only top off the fish tank with water and never dump and replace it unless there is a severe, unexpected problem. Why on earth would you get rid of all that beautiful fish waste? The notion of nutrient imbalance is as foreign to an aquaponic gardener as it is to an organic soil gardener. Just as with healthy soil, a healthy aquaponics system just keeps getting better and better the longer it operates.
The disease feared the most with hydroponics is a fungus called pythium, which is widely considered the scourge of hydroponics. Fortunately, pythium is almost non-existent in aquaponics. Researchers in Australia are currently studying why this is so, but it is likely due to all the bacteria and other living organisms in an aquaponics system. Logically they would help boost immunity; just as bacteria helps boost our own body’s immunity. Hydroponics is more of a boy in the bubble by comparison. In addition, the very high oxygen levels in an aquaponics system and the activity of the composting worms to clean up dead plant matter probably both help mitigate disease outbreaks. Hence again, Aquaponics appears to be the better choice.
An important part of an effective program to prevent pythium outbreaks in hydroponics is to make sure that the nutrient solution doesnt get above 70 degrees. Warm water is a perfect breeding ground for fungus, so keeping the water temperature below optimal breeding conditions for pythium makes sense. In aquaponics, however, the primary drivers of temperature are the requirements of the fish. The most widely used fish in North American aquaponics after goldfish, are tilapia, and tilapia does best in water that is between 80 and 86 degrees. The bacterium that drives the system is also happiest in that temperature range. Fortunately, because pythium is so rare in aquaponics this isnt an issue. The plants dont seem to mind either, as a report by Dr. Nick Savidov at the Crop Diversification Center in Alberta, Canada showed, aquaponics is every bit as effective at growing plants as hydroponics.
Optimal pH in a hydroponics system is 5.5 to 6.0. In aquaponics, pH is another factor that is compromised between the plants, fish and bacteria. Optimal pH is 6.8 7.0, which is again more closely related to what an organic soil gardener would target.
You’ve probably guessed by now that because aquaponics is an organic system that uses fish, special care needs to be taken with regard to insect control. Even commonly used organic sprays such as insecticidal soap or neem oil could be harmful if over-sprayed into the fish tank. On the plus side, however, you can engage your fish in your insect control efforts. If I have an insect problem on a small plant, such as young peppers or salad greens, remove them from the grow bed and let them soak in the fish tank for up to an hour. The bugs eventually loosen their grip on the plant and become fish food. And if you are lucky, the fish may even accelerate the process by nibbling the bugs directly off your plants. Another great idea is to hung Bug Zappers over the fish tank as an additional form of feed for your fish. This way you zap the pests before they even get onto your plants.
Hydroponics is a system for growing plants under highly optimized and technical conditions. Aquaponics creates a complete eco-system in which various living creatures all interact to create a symbiotic closed-loop system. We use worms, liquid seaweed and beneficial insects as each with jobs to perform rather than trying to isolate the plants and nutrients into single, definable, segregated components. Aquaponics is, above all else, an ecosystem where plants, fish, bacteria, and worms all live together in a beautifully balanced symbiotic relationship.
Start up Speed
This is perhaps the only downside to aquaponics from a hydroponics perspective. In hydroponics you just add commercially formulated nutrients to your nutrient reservoir and you are off to the races. With aquaponics it takes about a month to start your system by developing a colony of nitrifying bacteria through a process called cycling. The ammonia from the fish waste will not be converted into the nitrates that the plants are seeking until this process is complete. Still once it begins, the cycle lasts forever and is a beautiful feat of nature.
John Callahan is a consultant and contributing writer for the Aquaponic industry, you can learn more about him at reCALIBRATEYOURSELF.COM