The Development of the
Rice Lane City Farm Aquaponics System
An Awards For All project
Funded by The Big Lottery
Managed by Urbanag CIC
Copyright © 2014
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R
ice Lane City Farm, which covers some 24
acres of land including the former Walton
Park Cemetry in North Liverpool, utilises
its land well. Accordingly our options for locating the
aquaponics system were limited. The system’s tanks had
to be near a water supply, drainage and a power supply.
We also had to pay attention to the system’s safety.
The fish tank contains a large quantity of water. Even
with a cover it would still be potentially hazardous and
needed to be positioned away from the farm’s public
areas. The power cable to the system’s pump also
needed to be protected from public access.
Yet the system was always meant to be viewable by the
public.
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The chosen site was a general storage area - or dump adjacent to the farm’s administration and meeting block
(see picture 1). Before we could start work, we had to
find another area to house the miscellaneous contents
of the site. The fish and plant tanks that formed the
main elements of the aquaponics system would also
have to be separated by a fence from a public footpath.
Eventually, this fence would be replaced with a ‘seethrough’ barrier allowing the public to view the and the
barrier. Once the site was cleared we could start planning
the space to house the aquaponics system. Clearing the
site revealed a dead tree stump that presented a further
obstacle (see picture 2).
The stump would have been difficult to remove and
we decided to incorporate it into the system layout. It the soil with sand (over a ton of it) to allow us to even
was also a handy seat when taking much needed breaks out the surface with stones and flagstones. We saved
during the clearance.
money here by using recycled flags and stones
1 The storage area selected as our site showing the windows of the meeting room and existing fence.
The exposed surface of the site was soil; mud when it provided by the farm, and laid them around the tree
rained. To make a suitable base for the tanks we covered stump (see picture 3).
2 The tree stump revealed.
2 The cleared site with the tree stump in the middle of a layer of sand.
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3 The paved surface with the grey vegetable tanks ready.
The next stage was to install the tanks. The tanks were
the largest the site could accommodate while allowing
maintenance and leaving room for small groups to be
trained in using the facility.
The first tanks we acquired were for plants. These are
considerably smaller than the fish tank - which was the
largest we could fit in (see pictures 3 and 4).
With the floor of the aquaponics enclosure now in place
and the tanks on site we can now begin the process of
putting it altogether.
Health and safety issues
Since the site will be open to the public, health and safety
issues are of prime concern. These issues include:
1.
The system features a large tank which will
be full of water with (insulated) electrically powered
apparatus in and around the tank. There should be
no possibility of anyone falling into the tank even
if they have entered the system enclosure without
authorisation.
2.
The risk of electrical faults must be minimized;
the risk of damage, whether accidental or intentional,
to cables and switches must be minimized.
3.
The fish that are an essential part of the system
are livestock and their welfare must be considered at all
times.
The four main construction tasks
1.
The construction of a secure top for the fish
tank which allows access to the tank interior as and
when required. Access apart, the top of the tank must
allow the water to be exposed to light and air in order
to help maintain water quality.
2.
The installation of the vegetation tanks and
placing of the main filter (in size and shape similar to a
small tank).
3.
Wiring the various electrical components so
they can be controlled from a single point and do not
obstruct movement around and access to the site.
4.
Installation of the plumbing to join the various
component units together with minimum obstruction
to movement and access by people to the site.
4 The fish tank on its side.
Once in the area, we were reassured to discover that
our calculations had been right and the tank fitted very
nicely (see picture 5).
The fish tank
5 Fish tank on site and inverted for safety.
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The first task is to place the fish tank. A mat of
insulating material is laid between the tank and the
ground. The blue grey line at bottom of the fish tank in
picture 6 is the insulation mat.
6 Insulating the fish tank.
Although the mat may seem very thin for the job it will 8 Fish tank cover construction detail.
help the tank bed down once it is full of water (about 3
tons worth!). Unlike solids, bodies of liquid move with similarly sized step ladder). Our ladder also folds away
some force, and despite appearing to be very stiff and for easy storage (picture 9).
solid, a water tank can shift significantly once a weight
of liquid is added. Stability cannot be compromised.
It is important that daylight reaches the water in the
fish tank, so a slatted frame was made with an area
for an access hatch. The hatch is hinged and locked
unless access to the tank is required by staff. Only basic
woodwork techniques are necessary - if you can put
up a set of shelves or build flatpack furniture, you can
manage this cover (pictures 7 and 8).
9 The ladder in its fold away position.
Finally, since the tank is open to the elements it will
continue to fill when it rains and an overflow has been
fitted - shown in picture 10 - to drain excess water.
7 Fish tank cover with access hatch on left.
We bought a ladder to allow access to the inside of
the tank when a single slat is removed. When buying
the ladder for this purpose, make sure it has no cross
struts as is normal with step ladders. Cross struts would
prevent the ladder being placed close to the tank.
As the ladder has to be a bit stronger than an ordinary
step ladder to compensate for the lack of cross struts it
will cost more (we reckon it was twice the price of a
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10 The overflow pipe below the rim of the tank.
The vegetation tanks
tank was placed so the tanks were mounted on 2 x 4
The two tanks for the vegetables were placed as in (50 x 100 mm) wooden beams were bolted to the
conveniently as possible given the site restrictions. The ground at one end and levelled using foam spray at the
site also meant we were limited to two, although plans other end. Once this foam is dry it is very strong (see
to add more tanks inside a farm building are being picture 12).
The filter for the system is the shape of a box with pipes
considered.
sticking out. It was best to place this on the decking of
the fish tank as this would minimize the distance we
needed to plumb in the piping from the tank although it
did put it at some distance from the vegetables tanks. It
also had to be placed to facilitate servicing but to avoid
attracting inquisitive eyes and hands.
11 Upper vegetable tank mounted over the tree trunk.
The exterior location required a stepped support for the
tanks so water could easily flow from one to the other
and allow room for piping to be placed at the base of
the tanks. We used the tree stump as the base for the
upper tank (see picture 11).
Any exterior wood construction needs treatment to
protect it from the weather, unless the wood has already
been weatherproofed by the supplier. We used yacht
varnish on all surfaces as this is hard wearing
and designed to withstand the sort of extremes that
might affect yacht decking.
While nowhere near the weight of the fish tank, the
vegetable tanks still need to be secure as free as possible
from the risk of any accidental movement.
13 The overflow blockage protection system.
The vegetation tanks had drainage holes in their bases
which are not required. These have been covered by a
piece of piping equal in height to the tank’s, thus acting
as an overflow protection providing a return path for
excess water to the pumps (see picture 13).
12 Lower vegetable tank set level with expanding foam.
The ground was particularly uneven where the lower
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14 Three tanks in their final location.
We also used runoff from the nearby roof of the farm
building to act as a top up for the fish tanks but which
could be diverted when not required. The tanks have
been placed to allow access by small groups of learners
(see picture 14).
The electrical wiring
about 10 watts - the equivalent of a single low energy
light bulb. Despite the job the pumps do in moving
three tons of water around their power requirement is
moderate and could be delivered by pretty much any
domestic supply without the need for special power
arrangements other than a weatherproof switchbox
(see picture 17).
Before we started to develop the site to take the
aquaponics centre there was a single electrical cable
(see picture 15). This came from inside the building and
ran along the window ledge of the meeting room after
which it went underground across the public path to reemerge in the farm’s duck pond area to power the lights
there. Although it was well covered when the site was
used for storage, the cable was now exposed and there
was no conduit or cable housing around this cable at
any point between the exit from the building to going
beneath the path. This is considered poor practice and
is potentially dangerous. Accordingly, we decided to run
the cable through a conduit (see picture 16). The cable
carries the power that will drive the pumps and other
electrical equipment used for the aquaponics. It will also 16 Cable running through a conduit.
continue to supply power to the duck pond area.
15 Electrical cable before work began.
Two tank pumps will be used. These will run almost
continuously once the system comes into use as will
the autofeeder for the fish. The remaining apparatus
requiring power is a UV filter attached to the main filter.
This will only be used intermittently.
The two pumps require 65 watts of power each (about
the same as a single incandescent light bulb or about five
low energy bulbs). The UV filter and autofeeder require
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17 The control panel with the original power cable wired into it.
The panel has four outlets, all independently switchable. Note the
metal casing used to protect the input cable.
All cables need protection from the elements, creatures
prone to nibble at cables and accidental damage which
could make them dangerous to the public and wildlife.
Accordingly, all cabling is housed in a conduit.
Regulations allow for plastic or metal conduit to be fish tank. The main inputs are, therefore, electricity and
used. Plastic is both cheaper and easier to use, which is fish food.
why we chose it for this job. We used short lengths of
hosepipe to link sections of conduit where it would be
too awkward to run a conventional pipe. These need to
be sealed with tape or plastic foam (see picture 18).
The wiring created no problems although care had to
be taken to keep track of which cables were in which
conduit as in most cases each tube carried more than
one cable.
It’s useful to label each end of a cable noting its start
and end points, e.g. second left switch on control panel
to pump in fish tank.
19 A hose pipe/conduit junction waiting to be sealed with foam.
The pumps are submersible and need to be under water
at all times to prevent the bearings burning out. The
largest pump is located in the main fish growing tank.
Placing this pump as centrally as possible means it
benefits from and assists with centrifugal movement of
18 The power box with all cables fitted. We replaced metal cable water and fish waste, keeping the tank water clearer.
casing with plastic conduit and lengths of yellow hosepipe.
The discharge water is fed by a flexible 25mm diameter
hose to the higher level plant tank (where the water is
Although the conduit should be waterproof, to be filtered and processed).
doubly safe make sure there is no exposed or open
wiring inside the tubes. Condensation can build up and
cause problems.
On short and curved parts of circuit we used hose
pipes and sealed the ends with foam (see picture 19).
We used joints and junction boxes which allowed
inspection of the cables and access to the wiring should
repairs or adjustments be required at a later stage (see
picture 20).
The plumbing
20 An inspection box showing sections which can be unscrewed.
Junctions are glued to prevent the unit being pulled apart.
The system relies on gravity and two electrical pumps to
circulate water. Aquaponics involves a closed circuit in
which water containing fish waste is processed and used This pipe is secured to the pump and filter by thumb
as nutrient-rich plant food before being returned to the turn jubilee clips (see picture 21). Thumb turn clips
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are easier to use than the more common types which
require a screwdriver.
The water discharges in turn from the filter via a larger
50mm pipe (see picture 22). All pipework joints are
solvent welded (glued) for greater strength asnd to aid
avoiding leaks. The filter has two 50mm outlets with
one pipe fitted with a large in line value, to regulate flow
from the fish tank to flow to the first plant growing
tank.
The other discharge pipe acts as a bypass should the
plant tanks need to be taken off line and it also allows
surplus filtered water to return directly to the fish
rearing tank.
The water from the filter moves by gravity to the lower
plant tanks and although the water is not under great
pressure it is important that all joints are glued correctly
to prevent water loss.
The system has two growing tanks and water passes
from the first to the second again by gravity through
a 50mm standpipe which has been perforated to allow
the water level to be regulated.
The stand pipe is capped with netting to prevent growing
media entering the pipes and causing a blockage which
would be time consuming to clear on a regular basis.
21 A thumb clip pipe joint connecting the filter to the outflow pipe
taking water to the plant tanks.
23 The pump used to return water to the fish tank.
Once the water has passed through the second plant
bed it is returned to the fish tank by the second less
powerful pump which is connected by flexible hose
with thumb turn jubilee clips (see picture 23).
The remaining construction
All that remains is to place a thermometer on the fish
tank with probes monitoring water and air temperature
(see picture 24), and to cover the tank with a net to
stop leaves and other materials falling into the tank (see
22 The tap on the valve controlling the flow of water from the fish picture 25). Such foreign matter could degrade water
tank to the other tanks.
quality and negatively affect fish welfare.
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23 The thermometer secured to the fish tank.23 The
thermometer secured to the fish tank.23 The thermometer
secured to the fish tank.23 The thermometer secured to
the fish tank.23 The thermometer secured to the fish
tank.23 The thermometer secured to the fish tank.23
The thermometer secured to the fish tank.23 The
thermometer secured to the fish tank...PpPPP
24 The thermometer secured to the fish tank, with probes
measuring water and air temperature
25 Netting covering the fish tank and protecting it from leaves
and other polluting material.
Written, designed and
produced by Urbanag
Community Interest
Company
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