by Sally Morgan
If you are considering a small herd of dairy goats, then one of the best options for beginners is the Golden Guernsey – a friendly, docile breed that is smaller than other dairy breeds. They can be expected to yield 2-4 litres (3½-7 pints / 4¼-8½ US pints) of milk a day, which is a lower yield than from other breeds, but they also require less feed and have a better feed-to-milk conversion rate. The fat and protein content of the milk is perfect for making cheese and yoghurt. Once a goat has had her kids and they have been either removed or weaned (anything from 3 weeks to 3 months), she can be milked for up to 9 months, although the milk yield declines towards the end of this period.
Equipment-wise, you will need a milking stand and a clean area where you can milk, plus a stainless-steel milking bucket, udder cleaning wipes, milk filters and bags, as well as equipment and a suitable area for cheese-making. Once collected, the milk needs to be stored somewhere cool, where it is bagged up. With a small herd, milking is done by hand, so it can be quite time-consuming and of course has to be done every 12 hours.
Goats’ milk
Many people are turning to goats’ milk for its nutritional benefits. Compared with cows’ milk, it contains less lactose, while it has more fatty acids, calcium, potassium and vitamins A, B5 and C. It is also more nutritionally dense, so you do not have to drink so much of it to get the benefits. Its composition is closer to human milk than cows’ milk, so it is easier to digest, and people with allergies to cows’ milk can often tolerate goats’ milk as it has a different protein.
The meat goat
Goat meat is rising in popularity. It’s a healthy, lean meat, with a flavour more like game than lamb, but is still quite expensive, so raising a few kid goats for meat may be an option. The Boer is the traditional meat breed, as it has been bred with meat production in mind, with a good-sized frame and well-developed muscles.
Unless kept for breeding, most billy kids are raised for meat.
In many commercial dairy herds, male kids have no value and are often killed at birth. But this is changing as the market for goat meat increases, and increasingly they are sold to be raised for meat. Indeed, Boers are often crossed to a dairy breed to get better-quality male kids for meat. The kids are nursed for around 5 days, as this first milk from the new mother is not used by the dairy because of the high colostrum content, and then the dairy can earn some money from selling the kids.
Raising goat kids is time-intensive at the start, as the young kids are fed an artificial milk replacement until they are weaned. They are then moved to a diet of straw, hay and goat mix. They are raised for about 6 months, until they have reached around 35kg (77lb) in weight and are ready to be slaughtered. The finished carcass weighs around 15kg (33lb). The goats will have to be slaughtered at an abattoir, so check that your local one will take them.
Chapter TEN
Aquaponics
Aquaponics is a fascinating, simple and highly productive system that combines fish and plant crops. The dirty water from the fish tanks flows through grow beds, where bacteria convert the nutrients to a form that the plants can use. It doesn’t need much space, and you can even build your own DIY set-up.
Many years ago while on holiday in Kenya, I visited an innovative project based in an old cement quarry that was being restored by Dr Rene Haller, a Swiss environmentalist. The restoration work turned the derelict quarry from barren waste to a rich forest ecosystem, part of which is now a wildlife reserve. Alongside the restoration were numerous smaller projects to develop alternative technologies and promote organic farming methods. One of the projects was keeping fish.
They had built a series of fish ponds, with water draining from one to the next. The ponds were stocked with tilapia, and the dirty water drained to the lower ponds where the locals were growing Nile cabbage and rice. The water draining in turn from the vegetable plots was circulated back up the slope to the fish ponds. The plants took up the nitrogen from the water before it was circulated back to the fish. Surprisingly little water was lost, so this precious resource was recycled many times over. It was a very simple system, as many of these best ideas are, using appropriate technology. The fast-growing tilapia fish provided the locals with a valuable, but cheap, protein source plus a supply of rice and vegetables. Over the years the design has been improved and now the system includes chickens, whose droppings are fed to the fish! Today, we call such a system aquaponics.
An overhead view of the growing tanks and rearing pens at Baobab Farm in Kenya.
Aquaponics is attracting a lot of interest, and it is now much easier to get hold of both fish and equipment, and even to buy kits. It is a technical topic, so in this chapter I am offering just an introduction to the subject. If this overview sparks an interest, you will be able to find a wealth of more detailed information online and in books (see Resources).
A commercial system at Growing Power’s urban farm in Milwaukee, USA, which produces tilapia and yellow perch, watercress and tomatoes. The water is drawn through one pump and gravity-fed through the grow beds and back to the fish tanks.
Why aquaponics?
People have kept fish for thousands of years, both in ponds and in netted cages in shallow coastal waters. The disadvantage of rearing a large number of fish in ponds is the large amount of water polluted with fish waste that has to be discharged and replaced, so it is not surprising that growers looked to combining hydroponics – growing crop plants in soil-less culture – with aquaculture. Commercial aquaponic systems were established in both North America and Australia during the 1980s, soon followed by the development of smaller systems suitable for the garden or smallholding.
Aquaponics is a simple system comprising fish, plants and bacteria. The fish are kept in large tanks and their dirty water, laden with ammonia and other wastes, flows through grow beds, where nitrifying bacteria convert the ammonia first to nitrite and then to nitrates, a form of nitrogen that can be taken up by plant roots. The water is effectively filtered as it passes through the beds, and clean water is returned to the fish.
The circulation of water from fish to plants and back again can take place over and over again, with the only losses being from evaporation and transpiration from the leaves of the plants. It is a highly productive system, with plants growing up to three times faster than in soil and without the need for additional fertilizers. A small system has the potential over a 6-month period to yield about 25kg (55lb) of fish and many kilogrammes of vegetables from beds just 3m2 (32 sq ft).
The options
There are three main types of system suitable for a small-scale aquaponic system:
A media-based system is probably the most common, in which the plants are grown in beds of inert planting media, such as clay pellets or gravel. The bacteria form a biofilm over all the surfaces, both inert and living, that are in contact with water, and they convert ammonia in the water to nitrates. The planting media also filter the solid waste. The grow beds can be used to raise a wide range of crop plants, from salad leaves to aubergines, tomatoes and exotics.
The raft system is often the choice for people wanting to grow salads and other fast-growing crops. The waste water is filtered of solid waste and then pumped into a shallow channel, on which floats a foam raft. The plants are planted into the raft so that their roots dangle in the water, from which they take up nutrients.
Alternatively, the raft is suspended in a tank filled with circulating water from the fish tank.
The hybrid system is a cross between the media-based and the raft. The waste water is pumped first on to media beds, which remove the solid wastes, before being emptied into a raft system.
The media-based system is the most straightforward, and you can now buy complete kits (minus the fish) online. However, these can be quite expensive, and it is possible to make your own DIY system, which I describe on page 195.
A simple media-based system with flood-and-drain circulation. The water level in the fish tank falls as water is pumped out on to the grow bed,
and rises again as water drains back in.
A simple media-based system
This system consists of a large tank, which houses the fish, a grow bed filled with planting media, a pump and lengths of pipework. More tanks and grow beds can be included. The tank size determines the number of fish that you can raise, with a realistic stocking rate of 3kg of fish per 100 litres (6lb 10oz per 22 gallons / 26 US gallons). In turn, the number of fish determines the area of grow bed you can support (see page 198). The grow bed contains about 25-30cm (10-12") of media, such as gravel or clay pellets of a particle size around 8-15mm (¼-⅝”). The particles support the plant roots and provide a large surface area for colonization by nitrifying bacteria. The resulting cleaned water is returned to the fish tank. Regulation of the nitrogen levels throughout the system is critical to its smooth functioning, but, once the system is established and working well, it can run for months with just the occasional tweak.
The water is circulated in a number of ways. The simplest system is called flood and drain, whereby the grow bed is located higher than the fish tank, and a pump in the fish tank pushes the water up a standpipe into the grow bed, where it drains through the media and returns to the tank. With this arrangement, the water level in the fish tank varies (see diagram above). If the pump is located in a second tank, known as the sump tank, the water in the fish tank is maintained at a constant level (see diagram on page 196).
A tank of tilapia that is part of a media-based system.
The sump tank
A sump tank is needed as soon as the volume of the grow bed or beds exceeds the volume of the fish tank. The run-off from the grow bed accumulates in the sump tank, so it has to be positioned lower than the grow bed. It allows the water in the fish tank to be maintained at a constant level, which is better for the fish and means more water can be added to the system, which helps to maintain stability.
A sump tank works on this basis: at the start, the fish tank and sump are full of water and the grow bed is empty. When the pump starts working, water is moved from the sump to the fish tank, raising its level and letting water flow out into the grow bed. The grow bed fills with water and starts to drain out into the sump. Once the grow bed is full, the pump stops and the water finishes draining back out into the sump. In some systems, the pump is on all the time, keeping the grow bed in constant flood.
Temperature considerations
In a climate such as that of northern Europe, you have to decide whether you run the system year-round or just during the warmer months. If you do wish to run it all year, you will need heating for the fish tanks and also additional lighting for your media beds in order to maintain plant growth through the shorter days of winter. Many people setting up a system for the first time choose to grow carp or perch, either in a polytunnel, greenhouse or outside, and run the system from spring to autumn. The fish survive over winter, but as the temperatures are too low they do not grow, and need little food or oxygen; then they pick up again when the weather gets warmer in spring.
If you decide on a year-round system, choose carp or tilapia. Tilapia need a constant 25-30°C (77-86°F), so in temperate climates their water will need to be heated so they can survive and grow all year. The heating cost is the second largest expense after the fish food, but can be reduced by careful design of the structure in which the fish are kept. You could use an insulated polytunnel or adapt a brick building, for example. You could use photovoltaic panels to heat the water, with an electric water heater as a back-up. Don’t forget that your electrical system will be required to power not only the pump but also the lighting, and probably to meet at least some of the heating demand.
Choosing your fish
There are a number of options when it comes to the fish, but some are better suited to a small-scale system and are more resilient.
Tilapia
If you are setting up a system for the first time, you would be wise to opt for an easy fish such as tilapia, but, as already mentioned, they do require heated water. Tilapia is the most widely raised fish in aquaponics systems because it grows fast, is relatively tolerant of water conditions, and the fingerlings (young fish) are easy to source, as is their food. The fish reach a market able size of around 500g (1lb) in just 6 months, so it’s possible to stock a system in spring and harvest in autumn.
Red tilapia
Carp
This is an easy fish to grow, with a fast growth rate, but it’s not to everybody’s taste. The optimal temperature to raise carp is 20-24°C (68-75°F), but they do not need heating. As temperatures fall, so does their growth rate, so they can take a year or sometimes longer to reach a harvestable size. They can be grown in outdoor pools too (see page 199.
Carp
Rainbow trout
A fast-growing fish, the rainbow trout requires a high-quality protein diet and good-quality water. The ideal water temperature is 14-16°C (57-61°F), but they will survive at lower temperatures. However, their growth rate falls both above and below this temperature range. The fish take up to 10 months to reach size.
Trout
Perch
This species has a relatively fast growth rate and needs a high-quality protein diet. The optimum temperature range is 16-20°C (61-68°F), but heating is not essential. Although perch is an easy fish to keep, it’s not to everybody’s taste.
Perch
Setting up a DIY tilapia system
By far the easiest system to build yourself is one based on the ubiquitous IBC (intermediate bulk container), each of which measures a cubic metre (35 cubic feet), with a capacity of 1,000 litres (220 gallons / 264 US gallons). They come with a supporting metal frame. They are found worldwide and can be picked up cheaply secondhand. A small system based on a fish tank made from one IBC would support 3m2 (32 sq ft) of grow beds. To make the fish tank, the top of the IBC is simply cut off for access, while two other IBCs are cut down to create the 3 x metre-square (3 x 11 sq ft) grow beds and the sump tank. As well as the IBCs you will need a water pump, air pump and air stone (see page 198), grow-bed supports (which could be concrete blocks and planks), growing media such as volcanic gravel or expanded clay, plumbing materials including pipes and connections, plus bits and bobs such as a fish net, weighing scales, tape measure (to measure fish growth), thermometer, shading materials and a water-testing kit. Also, depending on your location, you will need an electric or a photovoltaic-powered water heater.
The layout of a DIY three-bed system made from three IBCs and using a CHIFTPIST (‘constant height in fish tank pump in sump tank’) system.
The IBCs last longer if they are coated with a dark paint to reduce damage from UV light. Also, this means there is less light reaching the water to stimulate algal growth, and the fish are kept in more natural conditions. Better still, box the fish tank to keep direct sunlight off and provide a more constant water temperature. You could add some floating plants to create shade and hiding places.
Check the source of your IBC
CHECK THE LABEL on the IBC to see what was transported in it and make sure the contents won’t harm your fish, as some toxic chemicals can contaminate the plastic. Even if the contents were safe, you must wash the tank thoroughly, and it’s easiest to do this out of the frame.
Water circulation
There are various ways of circulating the water, and the one suggested for this system is called CHIFTPIST (constant height in fish tank pump in sump tank). First, the water is pumped from the sump tank into the fish tank. To keep the water level in the fish tank constant, an overflow pipe carries the water to the grow beds. This pipe is called a SLO (solids lift overflow), and it extends to the base of the fish tank so it will draw up any solid wastes that have dropped to the bottom. The grow beds fill with water, and when they are full the autosiphon empties the water into the sump tank and the beds start filling with water again.
Typically, there is a flood and drain every 15 to 30 minutes, keeping the grow beds oxygenated for the plant roots and bacteria.
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The grow beds
These are made by cutting down two IBCs to form three beds of 35cm (14") depth (two beds come from one IBC – one from the top; another from the bottom). They are filled with growing media to within 5-10cm (2-4") of the top. It’s best to use 8-15mm (¼-⅝") particles. If the particles are too small, there will be too few air spaces, and these are essential for oxygen to reach the roots and bacteria. I prefer to use expanded clay, as the particles are lightweight and create a large surface area. They will not interfere with the water pH, but they are expensive to buy. Crushed rock or gravel is cheaper, but is also much heavier, and you also need to check that it does not interfere with the water pH, which can happen if using crushed limestone.
You need to get the beds planted up quickly, as the whole system depends on healthy plant roots taking up the nutrients. Using transplants is a quick and reliable method. Wash off the potting compost from the plants’ roots, so you don’t contaminate your system. These will be productive beds, so don’t waste the space: use closer planting distances than you would in vegetable beds. Aim to grow successionally too – as soon as the plants are of harvestable size they should be removed and replaced, to make good use of the continuous nutrient supply. Productivity can be high: for example, expect to be able to harvest 20 heads of lettuce or 3kg (6lb 10oz) of tomatoes per square metre (11 sq ft) per month in summer.