The Humble by Nature Greenhouse

We are just back from a fantastic couple of days with the team at Humble by Nature – lovely aquaponics set up with a side order of Black Solider Flies.  After doing a bit of filming we installed a wifi enabled WaterElf monitoring system in the greenhouse.  The only downside was the sound of the cockerels competing for attention outside our tents at 6am each morning, but it was a small price to pay!

Nitrate Deficiency in Aquaponics

It has been a few months since we started the University of Sheffield aquaponics system and the plants have been developing really well:

Nitrate post 1

Although a closer look reveals something else! Last week one of our team members found out there was a kind of yellowing developing in some of our plants.

Nitrate post 2

We set out to investigate what could be causing it and how we would sort it out.

First we examined the affected plants to look for obvious pests or other diseases and there were none. So it is probably some kind of toxicity or deficiency. As the system is new and toxicities are rare in aquaponics systems we supposed it is a deficiency. The complication is that there are more than a dozen possible nutrients so we need to follow a methodical approach to find out which one(s) are deficient.

The first thing to do to identify the missing nutrient is find out if the more affected leaves are new growth / upper leaves or the old growth / lower leaves. In our case the old growth was more affected.

This means the issue is possibly a mobile nutrient (instead of an immobile nutrient); a mobile nutrient has the ability to move from the old leaves to the new ones to support the plant development therefore the old leaves show the symptoms first. Great! This eliminates almost half of the possible nutrients.

Then the next step to follow is evaluate if:

A- The yellowing is on the entire leaf.

Nitrate post 3

B- The yellowing is more pronounced but the leaf’s veins keep a green look.

Nitrate post 4

Option A is our case.

The final step is defining if the plant has necrotic stop (dead tissue) or not.

Nitrate post 5

As our leaves show no signs of dead spots the most likely nutrient missing is nitrogen / nitrate.

This is a very interesting result:

On one hand this is an expected outcome as we are feeding our system 3 grams of fish feed per metre square per day and the normal range for a media based aquaponics without solid removal is somewhere between 10 grams to 40 grams (the exact quantity will depend in plant growth/light intensity/plant type)

On the other hand the nitrate concentration is 20 ppm (parts per million) using a liquid test (API Fresh Water) and 50 ppm using a dip strip (6 in 1 Tetra test). This range is not necessarily low for aquaponics.

We will test our assumption by increasing the feeding quantities and checking the results in the following weeks.


Three Key Issues with Conventional Farming and How Aquaponics Can Help

Conventional agricultural practices have made it possible for us to provide over seven billion people with food. This is a great achievement, however, there are more than a few problems associated with the current system. Not only does it have direct negative environmental impacts, it is also unsustainable in the long term. Thus, in order to secure the future of  coming generations we must find alternative solutions.

So how does aquaponics come in the picture? Surely, we are not suggesting that we should stop using agricultural land and grow all our food in aquaponic systems. But we do believe that this technology can play an important role in producing more food sustainably, and that together with changes in the way we use land, transport, store and – perhaps most importantly – think of our food, it could help us achieve food security in the future.

So, what’s wrong with conventional farming and how is aquaponics different? Here are my top three reasons why we should come up with a new strategy for producing food and what role aqaponics could play in it.

1. Takes up lots of space

We have already converted around 50% of habitable land on Earth to farmland, which has significantly contributed to the loss of species and natural habitats. In order to meet the increasing demands of a growing population more and more land is being put to food production at the expense of biodiversity. In addition to putting many species in danger, conversion of natural areas like tropical rainforests also speeds up climate change, which in turn poses a threat to agriculture itself. Ironically, since more people will need not only more food but also more living space, this vicious circle will result in competition for land from urbanization and agriculture.

Aquaponics offers a means to producing more food without using up more land by spreading vertically instead, using “spare” urban spaces in and around buildings, or even below ground. As long as light (artificial light is just fine) is available, these systems can function perfectly well anywhere from the edge of a parking lot to a corner in the office on the 10th floor.

2. Inefficient and wasteful

Plants grown in the fields can only take up a portion of water and fertilizers applied. A simple reasons for this is that roots can only access a limited volume of soil and are therefore only able to absorb what is in their immediate surroundings. Although some nutrients are delivered to them by the mass flow of water, a lot will get washed away before they could be absorbed. Many ions, especially phosphates, also get bound to soil particles and become immobile, with the bulk of them remaining out of the plants’ reach. Since plant productivity is positively correlated with nutrient and water availability, in order to maximize yields we dump large amounts of fertilizers on fields and flood them with water. This is unsustainable for several reasons. On the one hand, production of nitrogen fertilizers is costly and consumes lots of energy, mainly from burning fossil fuels (I don’t need to explain why that’s a bad thing, do I?). On the other, phosphorus, the second most important nutrient for plants, is a finite resource: we get it from mining rock phosphates, which are running out at an alarming rate. As regards water use, irrigation messes up with the natural water cycle, threatening drinking water supplies and likely causing unpredictable changes in climate. To make things worse, intensive farming practices also lead to loss of soil productivity and erosion, rendering fields barren and unusable in the long run.

As opposed to conventional farming, aquaponics uses no fertilizer or, as a matter of fact, soil. Instead, plants are grown in a special medium consisting of clay balls infiltrated with water rich in nutrients. These are supplied by bacteria that convert fish waste into nitrates, an ideal source of nitrogen for most plants. This nutrient-rich solution is circulated throughout the system (i.e. fish tank + units containing plants), which means that all of it is freely accessible to the plants. Excessive watering is not necessary either, only the volume taken up by plants and losses due to evaporation need to be replaced. To put it short: no fertilizer, minimal water input, no nutrients wasted and maximum uptake efficiency resulting in high yields. If that wasn’t enough, aquaponic systems are also quite cheap to install and cost close to nothing to maintain, their sole expenses being those of the fish food, some low power water and air pumps, and the occasional bucket of water. Sounds like a fair deal, huh?

3. Polluting

Another issue with agriculture is its huge carbon footprint that results from the burning of fossil fuels for industrial fertilizer production and use in various machinery, not to mention long-distance transport of produce. High CO2 emissions, which contribute to global climate change, are only part of the problem, though. Chemicals applied to fields can get into the environment, polluting rivers and freshwater supplies and damaging natural habitats, poisoning animals or even humans. Pesticides and herbicides can leak into the groundwater and rivers and may eventually end up in the oceans, causing harm to ecosystems far away from the original source. Moreover, in the same way that antibiotics can’t make a difference and also kill “friendly bacteria” in our system, pesticides can often have negative effects on mutualistic fungi and bacteria living in the soil that, under normal circumstances, would help plants acquire nutrients or become more resistant to pathogens and harsh environments. Although fertilizers are not directly toxic, if they get into the environment they can disrupt ecosystems, which may have serious consequences.

In aquaponics a closed system is used, so normally nothing can get out into the environment. For the same reason, it is also unlikely that anything gets into the system, meaning that there is less need for disease and pest control. As mentioned earlier, this technology doesn’t rely on fertilizers and so does not add to the carbon footprint of the industry. Growing vegetables in the city also helps remove CO2 from the air, as well as contribute to lowering emissions from transportation of food (there is no need for it if it’s all grown on your doorstep!).

So, what are we waiting for? Let’s grow a sustainable future with aquaponics!

Aquaponics and self-sufficiency

ReGen Village Netherlands Aquaponics

A number of recent articles (e.g. and have highlighted the efforts of Californian company ReGen to develop a demonstrator village of 100 self-sufficient homes in the Netherlands.  ReGen then plans to build more villages in Sweden, Norway, Germany and Denmark.

ReGen’s self-sufficiency model estimates that a family of three would need 639m2 to live in and provide for all of its water, energy, food and waste processing needs. Given that according to a 2012 survey the average UK home is around 92m2, comparatively 639m2 sounds like quite a lot of space.  However, it includes 120m2 of living space, and can be arranged vertically to reduce the footprint.  ReGen also estimate that the same family of three would need 8,100m2 of land to support themselves using conventional agriculture, making their system nearly 13 times more space efficient.

Of course the interesting aspect for us is that the ReGen model includes 300m2 of Aquaponics to produce fish and plant crops, and a Black Soldier Fly based waste processing system.  Black Soldier Fly grubs are incredibly efficient at eating organic waste, such as waste food and kitchen scraps.  When the grubs have had their fill, what remains is a well-mixed low-odour soil enhancer that can be composted or further processed to produce biogas.  Most importantly however, the grubs themselves provide a high protein food source for the fish in the aquaponics system.  This means that levels of environmentally damaging fishmeal used to produce commercial fish food can be reduced and even eliminated, creating a ‘closed-loop’ system where waste is turned into food and energy. Very neat.

ReGen Village Model 2

This approach is seen as a way to produce more resilient communities that have some protection from climate change with less environmental impact, and to provide a higher quality of life.  ReGen’s goal is to increase political will to make their self-sufficient development model mainstream in the developed and developing world. Of course this is the tricky bit, particularly the UK.  Brexit, our entrenched housebuilding industry, and high land prices are all obstacles.

However, we don’t have to compete with housebuilders for prime development land. Sinus Lynge of EFFEKT architects who helped develop the ReGen model talks about the fact that giving up space to food in inner city areas is “unthinkable”, but is it really?  There are currently some great UK examples of urban farming and aquaponics, such as Growing Underground and GrowUp, that are blazing the trail to demonstrate the scalability and affordability of such urban farms.  What we need is more of them, and fast. Of particular importance is demonstrating the viability of urban aquaponics schemes that have been ‘retrofitted’ into disused or underutilised buildings, on the roofs of occupied buildings, or even underground. Developing such opportunistic urban niches is the way to sway local and national political will, and arguably a more effective way of connecting with more people than the semi-rural villages depicted in ReGen’s images. Perhaps then the next list of proposed ReGen villages might also include city-based projects in the UK.

EU has already used up fish supplies for 2016

Name-a-fish3 - pair

Announced by The NEF (New Economics Foundation), last week saw ‘fish dependence day’ the annual day where EU fish consumption exceeds domestic fish production. From now until the end of the year,, All fish consumed by EU nations will have to be imported.
Aside from issues with air miles and carbon emissions, importing food is not necessarily a bad thing as it maintains important trading relationships and allows nations play to their strengths in terms of efficient production.

However, the EU has a bit of a fishy problem. Many European fish stocks are already overfished, and have been for several years as a result of increasing fish consumption in the EU over the past 50 years. In response to this, imports from non­EU nations have also increased over this time. However, whilst the EU enforces fairly strict regulations in attempt maintain a sustainable fishing regime, international fisheries lack the implementation of such regulations, which as well as being unsustainable has depleted local communities of their own fish stocks, as well as playing complete havoc on ecosystems and food chains.

But don’t worry, It’s not all bad news! Firstly, UK fish dependence day is forecast for the 19th of September this year, meaning the UK is more self­ sufficient than the EU as a whole (nice to know in the midst of post­Brexit madness!) Also, the proportion of overfished EU fish stocks has decreased since 2006 as a result of reduced fish dependence in the EU.

This announcement really highlights the need for alternative sources of food, which is where aquaponics has huge potential to contribute significantly to reducing sole reliance on EU and international fish stocks, and increase focus and production efforts of locally sourced food ­ no oceans required! :­)

So what do we think? IS aquaponics the answer? What contribution could aquaponics make to this? And how do we bring about change to implement these alternative sources?

Aquaponics: why bother? (Part 1)


A discussion with a member of the public in the Winter Gardens whilst feeding the fish prompted me to write this blog post to share the motivations of trying to develop aquaponics in Sheffield, and the UK.

As the global population spirals towards its predicted value of 9.2 billion by 2050, demand on global food production systems will be greater than ever before, whilst forecast climatic changes, increasing global temperatures and more extreme weather events will further impede crop yield successes, making it more difficult to maintain, let alone increase global food production. This is a massive issue — can we really make a different? Or is it such a huge disaster there’s no point in bothering?

Aquaponics comes into this as a ‘bottom-up’, community based approach in contribution to resilience in society. it isn’t a new concept: ancient Chinese communities commonly reared fish in the shallow rice paddy waters. Recently the technique has started spreading in Western society as a potential contributor to the emerging trend of urban farming and food production, something that will likely proliferate hugely in the near future as cities and urban populations expand and as long distance and polluting food supply chains become less and less viable.

Although widely used and well established in south-east Asia, information about and accessibility of aquaponics in temperate western climates is relatively lacking. By developing systems here, we hope to make aquaponics systems simple and cheap to install and run, making them a viable option to contribute to food security and social resilience. We’re not aiming to solve the global agricultural crisis, nor are we promising to feed a nation on tilapia and leafy greens 🙂  but hope to contribute to making aquaponics accessible,  more widespread and a socially accepted method of food production, with a focus on freshness, quality, and local produce, with minimal inputs and little waste.

But how can we change perceptions and behaviour towards food production and consumption, and spread aquaponics? Watch this space for my next article!

And where are the bacteria..?

This is one of the most frequently asked questions we get from people about our recently installed aquaponic system opposite the Students’ Union of the University of Sheffield.


And the answer is usually something like this: “Well, you know, in the water. Probably everywhere – we think so, at least.” And that is about as much as we could say. The truth is, we don’t know much about where they are, what they are doing, how many of them there are or what exact strains we have got in the system. (In our defence, it’s not easy to tell with microscopic organisms without the necessary lab equipment!) All we know for sure is that they are there and are doing a pretty good job.

But wait a minute. If they are invisible, how can we be sure they really are there? That is a fair question – but one we have a fair answer for, too.

Despite their minute size, nitrifying bacteria are key players in aquaponics. They are responsible for converting nitrogenous waste produced by fish into readily available nutrients that can then be absorbed by plants. To be more exact, ammonia is first turned into nitrites by a certain type of bacteria, which is then further metabolised into nitrates by another, providing a form of nitrogen suitable for plant uptake. Measuring the concentrations of these compounds in the water using some basic equipment can give an idea of whether and how much conversion is taking place.


If there were no bacteria present, we would find virtually no nitrites or nitrates and an ever increasing level of ammonia from fish waste (not to mention far-from-healthy-looking plants as a result of nutrient deprivation). In contrast, in our system we get constant, low levels of ammonia, no nitrites and slightly variable, but usually fairly high concentrations of nitrates, as well as healthy, fast-growing vegetables. As far as we know, this can only be explained by simultaneous removal of ammonia and production of nitrates, something that neither fish nor plants are capable of doing, which clearly suggests the involvement of an invisible third party.

OK. So they are there, doing whatever it is that nitrifying bacteria do, supplying nutrients for our plants in the process. But how did they get there in the first place? First of all we created a welcoming environment, using expanded clay balls for our grow media:


These balls have a very high surface area, so there’s lots of space for the bacteria to take hold (if they want to, that is – they might prefer floating around, we are not sure). Then we added a little powdered fish food (before there were any fish in the system) to create some ammonia for the bacteria to feed on, and finally a little vermicompost we hoped would contain some suitable bacterial populations. Yes, we know it is not exactly what you would call a reliable way of introducing the right microorganisms to the system, but as they don’t sell nitrifying bacteria in little test tubes in garden centres (yet…), this seemed to be the most workable solution. And then all we had to do was add some fish and seedlings and wait for the bacteria to start doing their job. And… hey presto! There they were 🙂  At least we think so!