Aquaponics Vs Hydroponics
On April 1st I gave a presentation at the Progressive Gardening Trade Association annual conference titled ‘Secrets to Selling Aquaponic’. The audience was primarily owners and managers of hydroponic stores.
When I was preparing and starting to think about the notion of ‘selling’ aquaponic, the first thoughts in my business school-trained brain were about target markets. How is the typical buyer of home aquaponics different than the typical market for these hydroponic businesses?
That thought, however, was immediately crowded out by a second, more basic thought. In order to sell aquaponic to a hydroponics customer, you really need to understand how aquaponic differs from hydroponics – which leads me to the point of this article. How does aquaponic differ from hydroponics? Let me count the ways:
Aquaponic vs Hydroponics
1. Startup speed – This is perhaps the biggest downside to aquaponic from a hydroponics perspective. In hydroponics you just add commercially formulated nutrients to your nutrient reservoir and you are off to the races. With aquaponic 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.
2. Relationship with bacteria – Hydroponic systems tend to be fairly sterile. I’ve visited hydroponic Groing facilities where I had to wear coveralls and a hairnet to enter. Not so with aquaponics. Bacteria are revered by aquaponic gardeners because, as described above, they are the engine that drives our systems.
3. Flood and Drain cycle – Hydroponic Gro-ers using flood and drain techniques generally only fertilize their plants once every four to six hours. Academic studies and vast, 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 Gro 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.
4. Gro bed depth – Hydroponic Groers tend to use standard 6″ deep flood tables and put pots or cubes with plants in them in
AquaBundance Aquaponics Gro Bed
the flood trays. Again, because an aquaponics Gro 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″ deep Gro beds filled with an inert media. Over the years, side by side trials have shown that this depth of Gro 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.
5. Nutrients ( supplementation) – 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 Groth could, and probably will, harm the fish and possibly the bacteria colony and the compost worms. There are a few exceptions to this, including the use of liquid seaweed, small amounts of chelated iron, and a few minerals to adjust pH. But beyond those, aquaponic gardeners will think long and hard before adding anything to their systems except of course, fish feed.
6. Nutrients (dumping) – 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 up 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 aquaponic gardener would query. 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.
7. Plant disease – When I oversaw the plant Gro lab at AeroGro, we were constantly worried about disease. We sterilized anything that ever came into contact with the plants, their roots or the nutrient solution. The disease we feared the most was a fungus called pythium, or ‘root rot’, 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 my money is on 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.
8. Temperature – An important part of an effective program to prevent pythium outbreaks in hydroponics is to make sure that the nutrient solution doesn’t get above 70 degrees F. 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 82 degrees 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 isn’t an issue. The plants don’t seem to mind either, as a 2005 report by Dr. Nick Savidov at the Crop Diversification Center in Alberta, Canada showed, aquaponics is every bit as effective at Groing plants as hydroponics.
9. pH – 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.
10. EC – Along with pH and water temperature, EC is the other measure that is closely tracked in hydroponics. EC, or Electrical Conductivity, is a measurement of the salts in the nutrient reservoir, which tells the hydroponic gardener how concentrated the nutrient solution is. This works because hydroponic nutrients are generally delivered in mineral salt form. Aquaponic plants, on the other hand, are fed by the organic waste from the fish, which has very little salts. EC is therefore not a useful measurement for the concentration of nutrients in an aquaponics system. Aquaponics requires confidence in Mother Nature, rather than a managed system requiring intense control. Once a system has been constructed using a set of generally accepted ‘Rules of Thumb‘ and has been fully cycled (ammonia and nitrite levels have dropped to zero), the only measures an aquaponic gardener monitors are temperature, pH, and nitrates. If nitrates are low (close to zero), more fish should be added to the system. If nitrates are high (above 50) more Gro beds and/or plants should be added. It’s as simple as that.
11. Insect control – 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, I’ll remove them from the Gro 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. I also know of people who have even hung Bug Zappers over their fish tank as an additional form of feed for their fish.
12. Eco-system!! – Hydroponics is a system for Groing plants under highly optimized conditions. Aquaponics creates a complete eco-system in which various living creatures all interact to create a symbiotic whole. We use worms, liquid seaweed and beneficial insects as ‘team members’, 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.
Read more: here.