First Principles

First Principles

Hello and welcome to my fortnightly DigiLetter. It excites and honours me greatly to be able to share my passion with you in this way. For a little more context and background about me, please read my introductory interview with DigiLetter.

Aquaponics and its future progression is something I have dedicated my life to. In an effort to help clear up some of the myths and misconceptions surrounding aquaponics, I will do what I can to remain concise. The 'definitive reference' on aquaponics is indeed what I intend to create throughout this series. But if I am short on detail with some things, forgive me — I will endeavour to keep this behaviour relegated only to things that can safely be described as post-requisite (i.e. not core information). So, let us begin.

Introduction: Aquaponics

Fig. 1

The English noun 'aquaponics' comes to us as a modern marriage of word units, comprised of the Latin root 'aqua' (meaning 'water') and the Greek root 'ponic' (meaning 'to toil' or 'to put'). A translation might be 'to toil with water'. There are many examples of ancient forms of agroecology that could loosely be described as a 'precursor' to modern aquaponics. 3500 years ago the Aztecs of South America created raised mounds inside fenced-off, shallow lakes. By using mud, decaying vegetation, animal dung and even 'night soil' (human fertiliser), these damp, microbially active mounds produced a greater yield of food than other methods available at the time. Indeed, wars were fought over control of these relatively small areas of land.

6300 years ago, paddy fields were already in use in South-East Asia. As eels, loaches, carp and other species relocated to take advantage of this new environment — and as animal run-off from intensive farming reached the paddies — early farmers could not help but notice the increase in productivity. Early records exist to attest to efforts to maximise this relationship.

Technology is truly a marvelous thing, and Google's incredible 'Ngram Viewer' is amongst the most amazing of all. With over 30 million scanned books (increasing at a rate of 1,000 per day) going back 500 years, anyone can use this tool to investigate the etymology and usage of any term in selected languages. According to this method, it appears the term 'aquaponics' first arose in English literature in 1933. The subject received some mild attention at the time — but this was soon erased by WWII. From this point on there appears to be no further mention anywhere in English literature for another 3 decades. Is this another lesson from history, on the untold costs of war? I should probably think so. Intermittent literary interest appeared again from the 1960s-80s, but even then 5 years could pass without a single worldwide mention of the word in English literature. It appears that aquaponics began its ascent into modern mainstream consciousness around 1990. By the time the internet appeared there was no going back and aquaponics has enjoyed an exponential increase in exposure since.

Modern aquaponics bears little resemblance to the related methods mentioned earlier. Not only do we have access to better materials, but we also have access to science. Today we know that an aquaponicist is primarily a microbe farmer and furthermore we know that microbes are what power aquaponic systems. We know that an aquaponic system is a broad representation of the natural processes at work in a freshwater river. However, it is a representation that must include all surrounding ecosystems and associated biochemical processes — from what goes on below the silt at the bottom of the river to the farthest reaches of the riparian zone. Aquaponics is an exercise in bio-imitation. While we cannot hope to functionally achieve 'closed-loop bio-mimicry' in our own artificial environments, we can imitate the processes that we do understand to achieve the most efficient and functional representations that we can practically manage. We assess where our loops are not 'closed' in our aquaponics system and do what we can to mitigate them. Though a subject for another edition, feeding the fish in a sustainable manner is the largest of 'unclosed' gaps in aquaponics. Electrical input is another.
 
In Figure 1 we can see a simplified representation of the aquaponic cycle. In practice, all processes are permanently ongoing and have no specific order. The ultimate goal is clean but nutrient-rich water, healthy plants and healthy fish — combined in the same, semi-closed system. As you might begin to suspect, this is not quite as easy as it first sounds — or as 'simple' as many might want to promote. Having said that, I enjoy great success and you can too. With aquaponics, surpassing the output of traditional, similar sized soil gardens is a cinch and the simplest of goals to achieve. Another great thing about aquaponics is that there are no known aquaponic-specific or related diseases that pose a serious health risk to humans. The same cannot be said for all modern farming types and methods.

Fig. 2


In its most basic form an aquaponics system comprises of at least two main components: a fish tank and a grow-bed for the plants (Fig. 2). As the fish breathes and metabolises its food, it excretes waste in the form of ammonia (NH3). The water is pumped up into the grow-bed, where certain types of microbes live that can use the ammonia in the water as a food source. By oxidising the ammonia into nitrites and eventually nitrates, these microbes turn toxic ammonia into plant food — over a period of some 8-12 hours. In turn, the plants soak up the nitrates and provide further particulate filtering via their roots. Gravity eventually returns the water from the grow-bed to the fish tank and the cycle continues. By investigating the science behind these microbes – who they are and what they do – we can determine what kind of environment they need to be able to perform their duties at maximum efficiency. Once again, this will be a subject for a later edition.

Although in no way necessary for a successful system, I choose to manage my aquaponics systems in a number of very specific ways. Firstly, all of my aquaponic growing efforts go towards growing food. I use aquaponics only to grow edible fish and edible plants. Not surprisingly, this is substantially more difficult than choosing to grow less specific, hardy or non-edible varieties. All types of weeds, reeds, bushes etc. will thrive in an aquaponic system. Similarly, many animal species such as goldfish, loaches, turtles, carp, frogs and tadpoles will also thrive. However, these are not normally a traditional part of my diet. In this respect aquaponics can be more easily managed, by simply choosing to go with a purely aesthetic design, supported by rugged plants and animals. Such designs lend themselves well to situations where phytoremediation (water treatment) is required. However as stated, my focus will be on food.

Adam Tait

“Aquaponics: The Definitive Reference” by Adam Tait

Adam Tait's lifework has evolved into promoting sustainable living through bio-imitation. He will educate you on both the theoretical and practical as he helps you build your own aquaponics systems from scratch.

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Electrical and Food Safety

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.

Design: Scale and Layout

Design: Scale and layout.

Once again, welcome back to my fortnightly DigiLetter, 'Aquaponics: The Definitive Reference'. In this issue we will embark upon the most important part of any aquaponics journey — the initial design process itself.
 
Design:

When designing and building aquaponics systems, one piece of wisdom is to be remembered above all and kept foremost in your mind. It is known as the 'K.I.S.S.' principle:
 
Keep It Simple, Stupid.

Continuing with my tradition of quoting Wikipedia at least once per issue, “The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore simplicity should be a key goal in design and unnecessary complexity should be avoided”.

The intended longevity of an aquaponics system is what makes this particular design principle so important. Over the years I have witnessed thousands of design variations on aquaponics. While many design 'improvements' may appear constructive and useful on the surface, only very few amount to actual long-term positive and desirable benefits. Generally speaking, the simpler design alternative is almost always the preferable one. Unfortunately, most of the designs available on the internet lend themselves towards long-term maintenance problems. What makes aquaponics exceptionally difficult for a beginner is that like most things, you can only know by having designed, built and managed many different types of systems over many years. Auto-siphons are the ultimate example. Despite the fact that there is a simple, cheap and more reliable alternative (i.e. simple timers and a permanent drain, as described below), something along the lines of 80% of new systems appear to be designed with auto-siphons. Here I shall endeavour to demonstrate only the most efficient methods that I myself use.
 
Scale:

The first task is to decide whether your system will be indoor or outdoor. This will be the determining factor in how big or small your system will be. For a new system, the rule-of-thumb to follow is to aim for a 1:1 ratio of grow-bed to fish tank volume — a 100 litre fish tank needs 100 litres of grow-bed. Don't worry if you can't quite manage that right away – half (0.5:1) is enough to start with and you have at least a few weeks time to build up the biological load before a 1:1 ratio becomes a requirement. Mature and heavily stocked systems can require as much as double the grow-bed to fish tank volume (2:1) and additional bio-filtration — however no aquaponic system should ever be started out 'heavily stocked'. Grow-beds can be added later as the fish grow and the biological demand of the system increases.

Grow-beds should be at least 350mm (14 inches) or deeper if there is no other bio-filtration planned (more on that next issue). This depth allows for our microbes to fully escape the light that they hate so much, while also providing sufficient space for their required population. For various reasons, you should build the biggest system you reasonably can. One of those reasons is that the larger the system is, the more temperature-stable it will be. Another is that the larger the system is the easier it is to maintain water quality.

If you live in a climate where snow settles on the ground every year for a week or more — or your minimum annual air temperature is much below -4 Celcius (25 F) — then you may want to consider an indoor system. Water temperatures need to be kept high enough for both the microbes and the successful growth of the plants. Water temperature below 10 Celcius (50 F) is approaching survival-mode for most edible crops and, even more importantly, for our precious microbes.

An indoor or 100% covered system might be inside your house itself, but it could also be in a greenhouse, a shed or any external structure. Clearly the greatest limitation of indoor systems is the lack of sunlight. Greenhouses go some way towards mitigating this, but they still limit plant photosynthesis. LED grow-lighting is the only realistic solution to indoor growing. Using power-efficient LED grow-lights alongside natural light increases the overall photosynthesis and assists with enforcing seasons. By only using the LEDs to augment natural light and natural seasons (instead of using them strictly for intensive growing), a lot of power and money can be saved and a larger area can be serviced. As a result, for serious, large projects in cold climates probably the best solution is a system entirely inside a greenhouse with LEDs to compliment natural light. An active compost heap inside the greenhouse can help provide warmth and CO2 to the plants.

An outdoor system can be as large as a property itself. Just as an example, the largest vessel I have seen that was suitable as an aquaponics fish tank (a HDPE water tank) was 4600mm (15 ft) in diameter. At 1000mm (3.3 ft) deep this makes for a 17,000 litre (4500 gal) fish tank. At 350mm deep and 1000mm wide, this would require 50 meters of grow-beds and provide 50 square meters of planting space. This can grow to 100 square meters as the system matures and stocking density increases. Remember – the grow-bed area is just the planting area. The actual area that the plants can occupy is more than double that again. Commercial set-ups with even larger requirements can simply begin repeating and replicating this maximum size.
 
Layout:

Firstly, just like the auto-siphon we will do away with another common design addition that is actually just another unnecessary complication – a sump. The only semi-valid reason for considering using a sump is to ensure that the water level of the fish tank is kept at an exact and consistent level. To put it simply, this is unnecessary. Cyclic changes in maximum water level of less than 15% are completely acceptable and such minor variations are of no concern to the well-being of the fish – especially at depths of up to a meter. If it were, fish would be a lot less inclined to rise and fall in the water column voluntarily, as most fish do. Once again, this understanding and acceptance allows for simpler and therefore more resilient designs.

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Bio-filters, Microbes, Stands & More

Bio-filters, Microbes, Stands & More

Once again, welcome back to my twice-monthly DigiLetter, 'Aquaponics: The Definitive Reference'.

Recapping on my previous issues, by now you should have a good idea of where you want your aquaponics system located and what size it will be. You should know what type of grow-media you will be using – scoria/pumice/lava rock, expanded clay balls, gravel etc. – and where that grow-media can be sourced (not to mention how you will initially wash the media, prior to use). You know that appropriately sized, food-safe tanks for the fish and the grow-beds – such as HDPE rainwater tanks – need to located and acquired. I have covered the relative size ratios required of these vessels and I have also covered some of the basics of how they should be arranged and plumbed. So, what's next?
Stands


The grow-beds need to be raised quite a way to achieve a good water depth in the fish tank and one cannot stress enough the importance of strong and stable grow-bed stands. Since 1 litre of water equates to approximately 1 kilogram, grow-beds can be extremely heavy and as a result they are always going to be top-heavy. Besser blocks, concrete blocks, bricks, steel or thick timber are suitable materials to build stands for grow-beds.

 


The above image is a 600 litre grow-bed and stand, built by the author. This was a successful experiment in using thick HDPE liner, folded to shape and supported by the wooden frame as a grow-bed. Otherwise it was plumbed normally.

Earthworks are a solid solution for supporting grow-beds in large or commercial systems, at least for those with access to the machinery and know-how. For systems where aesthetics is an important element, 25mm extruded aluminium square tubing and associated fittings can be customised in a grid/matrix fashion to support unlimited grow-bed sizes, just by keeping all tube lengths to 450mm or less. With a suitable geometric layout of the beds and tanks, this can look quite striking when supporting a colour-coded rainwater tank aquaponic system especially after everything has been cut, customised and edged with black rubber tubing. Now, imagine it overflowing with plants and produce! Aquaponics doesn't have to be patched together out of recycled and second-hand goods. In fact, if you want it to last for decades and therefore appreciably contribute towards solving our global environmental problems, then it is definitely best to purchase new. Nothing will last like modern poly water tanks.

The maximum water depth of your fish tank is determined by the distance from the bottom of the fish tank up to the bottom of the grow-beds. This should be somewhere between 450mm and 1200mm, depending on the shape of the vessels and the desired fish tank volume. Any deeper and the bottom of the tank cannot be reached from the outside with a net, not to mention that the energy cost to push water up that high begins to add up (pump 'head'). This can become a problem down the track when expanding the system and trying to transfer over to a limited source of renewable energy. Furthermore, water depths over 1200mm mean the grow-beds end up being above a comfortable height for working on (that being somewhere between hip and chest height). Any shallower and managing water temperature becomes near impossible – not to mention the issue of going back to gardening on your knees! Personally, I prefer my fish tanks at just over 1 metre deep, maximum. Burying or recessing the fish tank into the ground is also a way to obtain good water depth without having to construct grow-bed stands that are too high and too unstable. Positioning the fish tank next to a retaining wall, verandah or other raised platform also allows for shorter and more stable grow-bed stands by having them on top of the raised platform.

Bio-filters

As discussed in the first issue, aquaponics is entirely powered by microbes – specifically, various species of bacteria and archaea. These are commonly referred to as AOMs – ammonia-oxidizing microbes. Sometimes they are also referred to as chemolithoautotrophs, however the only reason I mention that is simply to say chemolithoautotrophs. Wow.

Being such tiny organisms, they can (and will) inhabit every dark and damp nook-and-cranny in your aquaponic system – and the more the merrier. Indeed, this is the primary reason for the choice of flood-and-drain grow-beds in aquaponic systems. The deep media-filled beds provide just the habitat the AOMs are after, with plenty of surface area on the medium to colonise. While AOMs will be found throughout the water column and their generous population should change the water colour to a slight tanin-brown, they are not really 'working' at their best while submerged in open water. To be truly happy and efficient, they require a surface to attach to. Furthermore, water cannot provide enough oxygen for them to efficiently oxidise ammonia. No matter how hard you try, water has a maximum limit to its oxygen-carrying capacity and this is not a sufficient concentration for efficient ammonia-oxidation by these little helpers. Roaming AOMs and slight water colouration are just side-effects of having a healthy system with a large population.

Fish Tanks, Fish Species, Grow-Bed Types & More

Fish Tanks, Fish Species, Grow-Bed Types
& More


Hi folks – back again with another edition of my bi-monthly DigiLetter, “Aquaponics: The Definitive Reference”. Last issue, among other topics we looked into the importance of stands and the universal need for bio-filters in aquaponics. This issue we are going to start off with more about fish tanks and fish species, so let's get right to it.

Unless one chooses to implement used or second-hand items, there is little chance of finding a better, cheaper or more suitable product for use as a large-scale fish tank than HDPE rain-water tanks. The industry of rotational moulding behind these products is a mature one, with a long history and plenty of exposure to competition. This guarantees that there is no point looking elsewhere for suitable product alternatives. Large, food-safe vessels, designed to contain potable water and exist in outdoor conditions for decades, make up the core business of the roto-moulding industry. They come in sizes from under 300 litres to over 50,000 litres and are found in both rectangular and round configurations the world over. In some countries and jurisdictions (such as some places in the US) there are laws pertaining to rainwater collection and in these economies the roto-moulding industry is smaller. I was stunned to learn that this was actually true.
 

In the image above we can see a HDPE water tank altered and customised by the author. With a large access window cut high into the wall of the tank and lined with rubber hose, we can access and view our fish comfortably. All water tanks are rated to only 80% of their internal volume, so half the depth of a rainwater tank is more than half of its labelled rating. In the case of the 3000 litre tank pictured above, filling the tank with water to the bottom of the window is around 2,650 litres.

One of the truly great things about HDPE rain water tanks is just how big they can go. The property we purchased and moved into just over 12 months ago came with two enormous 50,000 litre tanks. Unfortunately, we use them for the purpose they were actually designed for and they are apparently off-limits for aquaponics (for now). The size of these vessels allows for agricultural-scale aquaponics systems. In the image below, filling the water tank to the level below the pipe access holes is around 12,000 litres. So far, this is my record for the largest fish tank.
 

One of the numerous advantages to using these tanks this way, is that they provide a semi-enclosed environment. This has many, many benefits such as: greater heat retention, reduction of evaporation, reduction of algae, protection from leaves and falling debris, hiding the fish from birds, providing nowhere for cats to perch and access the fish, reduction of 'escapees' (e.g. jumping trout or climbing crayfish species), ease of plumbing and last but certainly not least, it provides a structure from which to hang and support devices and objects. One such object should be a waterproof power distribution box (see edition #2).
 
Fish Species Selection

This is a very sensitive topic and one that I feel extremely passionate about. One of the single greatest environmental factors impacting on our waterways, is the human-assisted movement of aquatic species, to areas outside of their natural range.  Almost all major water-catchments on the planet are under enormous strain from the impact of one or more introduced 'noxious' species. Since there are literally too many examples to mention, I will relate just my own experience.

As a child I was brought up in country Victoria, Australia. Although I didn't know it at the time, the early 1980's marked the very end of widespread native fish in Victoria. The impact of the preceding 150 years of decimation had not properly sunk in to the minds of the general public, let alone me. In my earliest memories of our regular family fishing sojourns, Golden Perch, Murray Cod, River Blackfish and Silver Perch were all part of a day’s fishing. I thought that was normal. It turns out we were just fishing some of the last remaining native populations. Already, Redfin (European Perch) had taken over most inland waterways. Trout had displaced many species and decimated others with disease. By the mid-80's introduced carp had reached plague proportions and by the mid-1990's there simply were no more native fish to be found.

In the past 20 years desperate efforts have been undertaken by government – in partnership with universities, private industry and N.G.O's – to reverse this damage. Expectations were low in the beginning and many people including myself suspected that these unique animals and their unique environment were likely lost forever – another tragic case of too little, too late. But surprisingly, we have discovered that much can be done. Just like our careless and thoughtless actions have had such a pronounced effect on the environment in the past, so too can our targeted and thoughtful actions have a pronounced effect on the environment in the future. There are now many examples where native fish populations have demonstrated strong recovery alongside the diligent efforts of concerned scientists and individuals. Given a chance, most of our native species can adapt to new environmental scenarios. But it is only with thoughtfulness and care that we can make progress. No ecosystem and no species are truly lost until they are declared extinct and every location and every species on the planet alive today, still has a chance at a better environment. This is why fish species selection in aquaponics is so important. People will release fish into the wild, rather than kill them. Floods and structural failures will sweep fish away and into the wild.

No harm is done, only when these fish are an endemic, local species.

Australia is blessed with a broad biodiversity of freshwater fish species, but this is not entirely unique. All freshwater catchments of the world have their own list of endemic native species. These could be native species of trout, char, perch, bass, catfish, eel, crayfish, shrimp, mussels or any other related native species. As mentioned in previous editions, aquaponics doesn't have to be about growing food – but it is certainly better when it is. Edible fish species give your aquaponics system the protein output it otherwise lacks. If this native, local, edible species also happens to breed in a recirculating aquaculture system, then you have your perfect species.

Indeed, there are certain foreign species that will do incredibly in aquaponics – species like carp and tilapia. Some of these specimens can live in water quality approaching sewerage and quite literally live on a diet of mammal droppings. Believe it or not, every few months I hear of another 'revolution' in aquaponics, where the next person has worked out that some species of fish will actually live off Guinea Pig faeces. Without going into expansive detail, this is not a good idea. Besides the associated health implications of actually eating this stuff, it is these exact robust survival characteristics, that make these species so dangerous to a foreign ecosystem.
 
Other Grow-Bed Types

A robust aquaponics system of sufficient maturity and bio-filtration, can be viewed in the same way that a nutrient tank is viewed by a hydroponicist. In this sense, once all other bases are covered, an aquaponicist can start adding growing techniques usually limited only to nutrient-rich hydroponic applications – growing methods such as 'nutrient film technique' (NFT), 'deep water culture' (DWC) and even another
 

invention of mine: a 'vertical trickle bed'. I will give a brief description of each of these shortly.

In the early stages of an aquaponics system, the population of AOM's (see edition #4) is still expanding. As a result, the water is not nutrient-rich enough. Focussing on anything beyond increasing that population in deep, media-filled beds and bio-filters is a distraction. However once the fertility of the system reaches a certain point, such additions can be made. The single greatest benefit that these methods offer is that they require very little extra water from the fish tank, unlike the flood-and-drain beds. This means we can increase our growing capacity without having to increase our water volume.

Plumbing & Thermodynamics

Plumbing & Thermodynamics

Hi folks – back again with another edition of “Aquaponics: The Definitive Reference”. No doubt you are chomping at the bit for more information, so let’s get straight to it.
 
Plumbing

Plumbing in aquaponics can be broken down into two basic categories – the pipe and the fittings. Properly designing your system well in advance (on paper or in a computer) will allow for accurate estimations of the amount of plumbing materials you will need to purchase. As has been mentioned in edition #2, steer well clear of green garden hoses. This type of hose is not suitable for aquaponics and in no way should it be considered 'safe'.

Pictured are 3 types of pipe/hose considered suitable for permanent use in recirculating aquaponics systems:
  1. Black HDPE pipe (blue or green stripe):

  1. White rigid PVC-U pipe:

  1. Black reinforced flexible PVC hose:

All of these pipes and hoses are considered safe (and legal) for commercial aquaponic and food transport applications in Australia, as per the Australia/New Zealand Food Standards Code (Standard 1.4.1, and Standard 1.4.3).

While this specific information only applies directly to Australia/NZ, it does provide a prompt for people from other nations to seek out the relevant guidelines and authorities in their area. At the very least, using the products and materials suggested here will guarantee your personal health. Furthermore, it is very likely that these products will be considered legally suitable for commercial aquaponics systems in your country also.

'Standards Australia' has developed an Australian standard for plastic materials for food contact use, known as Australian Standard AS 2070 –1999. AS 2070 specifies a number of requirements that pipes and fittings will normally not meet because the standard addresses the manufacture and packaging of foods, rather than transport in piping systems (although that is not specifically stated).

Therefore, according to a document entitled “PVC and Polyethylene Pipe Systems for Food Transport Applications”, published by the Plastics Industry Pipe Association of Australia Limited in 2011:

“Product standards for PVC and Polyethylene pipes and fittings do not require conformance to AS 2070-1999 requirements, because a major application for these pipe systems is the transport of potable water at 20ยบ C and the performance requirements address this application.”

Specifics of the Australia New Zealand Food Standards Code – Standard 1.4.1 – 'Contaminants and Natural Toxicants' can be found at http://www.comlaw.gov.au/Details/F2011C00542.

Specifics of the Australia New Zealand Food Standards Code – Standard 1.4.3 – 'Articles and Materials in Contact with Food' can be found at http://www.comlaw.gov.au/Details/F2011C00542.

My personal preference in pipe/hose types is most certainly #3, the black reinforced flexible PVC hose. While most flexible PVC products are not suitable for food or water, purpose-built products such as food-safe vinyl tubing are available. The main advantage in an aquaponics setting is the smooth interior bore, combined with the lack of a requirement to install elbow-joiners for bends. This makes for very low internal back-pressure, allowing us to use the absolute minimum electrical energy required to achieve our desired water flow rate. This efficiency of water movement is true for both the delivery and return of water from the beds. Water returning rapidly to the tank under gravity imparts kinetic energy to the fish tank reservoir, which results in turbulence and improved aeration. This hose is non-kink, UV stabilised, abrasion resistant and suitable for fresh water or marine applications. Frankly it is as tough as nails and is not overly expensive.
 
Fittings

Plumbing fittings in aquaponics can be broken down into three basic categories – tank outlets, valves and joiners. When using the blue or green stripe black HDPE pipe or the rigid PVC, you are quite limited to what fittings you can use. There are particular fittings for both of these pipe types and not much else will sufficiently do the job. In this case, any plumbing supplies or hardware store should be able to help you out. Just be prepared for a shock when the total price arrives.

Flexible PVC hose can quite happily accept the similarly sized 'threaded' or 'barbed', push or screw-in joiners, valves and outlets. This is a great bonus because the fittings are cheap and many different fitting types can still give a water-tight seal with this type of hose.

For each grow-bed you will need two Nyglass (glass reinforced nylon) barbed tank outlets like this:




For each grow-bed, you will also need a single barbed inline poly valve, such as the 'Green Back' poly valves offered by Antelco:



 
Plumbing Sizes

This is very simple, as I have devised a straight-forward rule for plumbing sizes that applies to a very wide range of bed sizes:

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