Electrical and Food Safety
Welcome back to my fortnightly DigiLetter, 'Aquaponics: The Definitive Reference'. In the last edition we explored the basic principles of aquaponics. In this edition we will tackle something very important — practising aquaponics safely for the many years to come.
Longevity
Our health is all we have. People who have experienced serious and long-term illness can attest to this — as can anyone who has provided care for the gravely ill. Our physical and mental health should be of primary concern to us all. From this, all other things follow. As a response to this concern, people from all over the world are becoming increasingly interested in producing more of their own food at home. Home-grown food provides freshness that cannot be matched and it comes with a known history of contamination. While in the garden, home-grown food doesn’t spoil or require expensive refrigerated storage. It simply sits there growing until it is harvested as needed. In this modern age almost anything you grow and eat positively contributes towards a healthy diet. Home-grown food is not processed nor does it come with extra fat, high-fructose corn syrup, salt, preservatives, colours, flavour enhancers or emulsifiers. From just a personal perspective, I have lost almost 25% of my total body weight since relying more heavily on food that I produce. From a Body Mass Index of 31 ('Obese'), I eventually dropped to a BMI of 23 ('Healthy weight'). My statistical life expectancy has risen dramatically as a result. I feel better, I have more energy and apparently I no longer snore.
For these reasons and more, an ever-growing number of people are looking for better ways to access home-grown food. Aquaponics is well placed to meet this growing demand, but there are certain associated potential dangers that must be properly addressed. The consequences for failing to do so can be dramatic. Since aquaponics systems are designed for lifetimes measured in years, a lot of time will pass in which something can go wrong. It is also a long time for any toxic substance to build up, in what is a recirculating system. As a result, the two potential sources of danger from aquaponics are electrocution, and/or food contamination. Both are easily and completely avoidable and I will deal with each of these in turn, beginning with electrical safety.
Electrical Safety
Under most circumstances, mixing water and electricity is a bad idea. However, the pool and spa industry, the hydroponics industry, the aquarium industry and many others have proven that it can be done safely. All that is needed is a little education, a little common sense, a little forethought and a little money.
The two cardinal rules for dealing with a filled aquaponics system are:
- Never leave any electrical connections or power tools on the floor/ground.
In the event of a structural failure or leak, the area around the system will become submerged in water and any electrical connections at ground level will become saturated. All cable connections must be hung appropriately and power tools must be on a bench/chair/table at all times.
- Never join extension cables to make longer lengths. Always use single, full-length power cables.
Single length power cables are significantly safer than joining two together. Don’t use old cables, especially if you are planning on building an outdoor system. Purchase the thickest, highest quality, UV-stabilised power cables you can afford — at the right length for the job. Besides the ongoing danger of electrocution and the potential for fire, a power failure that goes undetected at the wrong time can pose a serious risk to the fish and plants. If left unattended long enough in hot weather, the plants will wilt and die from thirst and the fish will soon follow from lack of oxygen and poor water quality. In exceptionally hot conditions with a heavily stocked system, fatalities can begin in just a single afternoon. In the long-term, high-quality cables go a long way to increasing the likelihood of a continuous and uninterrupted power supply to the system.
Another common and serious problem is the issue of water running along power cables. Between gravity and surface tension, water can do some pretty amazing things. It can run along underneath horizontal objects for a surprising distance and condensation is a very likely source of such a random trickle. Power cables must be set up such that any water that falls on them cannot reach the end-plugs. Keep your power sources up high and run the cables inclined or vertically. If a decline is absolutely necessary, a vertical loop can be made to force water to drop off the cable.
I was once electrocuted by an aquaponics system due to a cheaply-made submersible pump. Somehow the pump had developed an electrical leakage and was charging the entire system. Luckily it was very wet during winter and the entire system was grounded. All I felt was a burning-tingling sensation as the charge went from the water and through me. The fish and plants didn't seem to mind at all. The moral here is to stay away from cheap devices. It's just not worth it.
For outdoor systems, there is the added problem of rain and wind. Ideally an outdoor aquaponic system running on mains power should be connected to a properly installed, IP-rated outdoor power point. However, running a power cable from inside the house or shed is perfectly acceptable, provided that a permanent solution for the protection of the cable itself is also considered. Ensure to avoid any crushing, jamming or bending of the cables in door jams or window frames. The low power requirement means that any available power point is sufficient and just one will do the job.
In an outdoor system wind is a significant factor. A swinging power cable will eventually wear through no matter how high quality it is. The main power cable should be properly secured and if running it up high it should be pulled taught to minimise movement. Placing the main cable in conduit and burying it is a neat option, if you are qualified to remove and replace the end-plugs of the power cable, to a water-tight standard. Otherwise a 50+ millimetre pipe is required to fit the end-plug through, which can be expensive over longer distances.
At the aquaponics end we set up an external water-proof power box to house a multi-plug power board. This should be kept as close to the system as is reasonable, so that every device in the system can reach the water-proofed power board using just its own cable. My power boxes are mounted to the outside of the fish tank itself, about 600mm above the water height. I recommend grabbing one of the many off-the-shelf solutions such as those pictured below which can found at many hardware, gardening and DIY stores:
I happen to use both of the boxes pictured and they perform very well. They are 100% weather-proof and show no signs of deteriorating two years after purchase. The left hand product is a better design, as although the right hand product has better features and better build quality it has a fatal flaw. If it is opened while it is still wet, then collected water runs inside. Make sure you mount them out of direct sunlight so that they don't over-heat in summer.
