In the past 50 years, the global demand for fish products has doubled, and more than 45 percent of the world’s seafood today now comes not from wild catches, but from either land-based or offshore fish farms. To meet this rising demand for seafood worldwide, more fish have to be raised in fish farms, and aquaculture is an essential link in the agricultural chain.

1. FISH FARMING TECHNOLOGY
A Breath of Fresh Air in Fish Farming
T
he Food and Agriculture Organisation, a United Nations agency, has recently
stressed the importance of fish farming, noting its place as the most sustainable
and fastest growing food sub-sector in the world. The organisation stated that
fish provide the world with 17 percent of its animal protein and emphasised the
importance of fish farming as a global trade.
However, with increased fish farming comes more responsibility from operators
to ensure that their farms are maintaining the best possible fish growing conditions;
including appropriate nutrition, prevention of disease and maintaining a healthy
water environment.
The importance of healthy water
The most important factor for achieving healthy fish is to have healthy water. Therefore, controlling the
concentration of oxygen dissolved in water is crucial in aquaculture. Maintaining the right level of oxygen
in water improves utilisation of feed, reduces fish mortality and reduces the need for vaccination and
antibiotics.
This is particularly important in sea cages. Though some have sufficient oxygen levels from surrounding
seawater, there are instances where this is not the case – particularly in locations experiencing rising water
temperatures that contain low levels of oxygen. As there is lower solubility of oxygen at higher water
temperatures, this situation becomes more critical during summer months than in winter.
Linde, the world’s largest industrial gases and gases engineering company has a long history of working
in the area of food security to give food processors and consumers the reassurance that the food they eat
is fresh, authentic and sustainable. The company has been supporting fish farmers through its SOLVOX®
In the past 50 years,
the global demand
for fish products has
doubled, and more
than 45 percent of the
world’s seafood today
now comes not from
wild catches, but from
either land-based or
offshore fish farms. To
meet this rising demand
for seafood worldwide,
more fish have to be
raised in fish farms,
and aquaculture is an
essential link in the
agricultural chain.
by Stefan Dullstein & Hans Joerg Meissner, Linde
50 | March | April 2016 - International Aquafeed

2. range of products, which comprises a variety of oxygen
dissolution and distribution systems, which offer a
comprehensive range of oxygen supply modes.
Late last year, the company introduced the latest in the
SOLVOX®
family – SOLVOX®
DropIn – which was
designed specifically to meet the need for oxygenation in
sea cages.
DropIn: A New Way of Delivering Oxygen
Representing an innovative and effective new way of
improving the delivery of oxygen into fish farming sea
cages, the pioneering “DropIn” technology was originally
developed for use in improving oxygenation during sea lice
treatment. It now also can also be used in sea cages which
experience unhealthy water conditions due to poor oxygen
levels or where supplementary oxygen is needed, including
in harvesting tanks.
The product was designed to be compact and lightweight
and highly portable, eliminating the need to drag perforated
hoses across cage floors. It comprises an electric pump
plus a patented oxygen dissolver and distribution system
featuring a venturi nozzle. SOLVOX®
DropIn distributes
oxygen evenly across a wide radius, delivering it in a
pinwheel form, which makes for more homogenous oxygen
throughout the cage.
The innovative design represents a break-through in
oxygen delivery and is the first of its kind on the market. It
provides 50kg of oxygen in the water at 2.2 kilowatts per
hour. Typically for the same amount, wastewater treatment
will use more than ten kilowatts per hour, which represents
a considerable step forward in terms of energy savings.
FISH FARMING TECHNOLOGY
Left hand page:
The Sovlox DropIn
aerator in action
Right hand page:
The Solvox DropIn
aerator
International Aquafeed - March | April 2016 | 51

3. Mitigating Sea Lice
Sea lice are parasites well known to the aquaculture
industry for posing a significant threat to fish farmers. They
can compromise the health of fish, and damage their hosts’
skin through feeding, causing lesions and infections through
viruses and bacteria. Though they occur naturally in the
marine environment, sea lice can represent a particular issue
among farmed fish where a more concentrated population
means that infestations can spread quickly.
If a sea lice concentration reaches above a certain
threshold, fish farmers need to apply treatments. In sea
cages, these can only be applied once the cages have been
completely wrapped in foil to maintain the necessary
concentration of delousing chemicals within the water.
However, as the foil cuts off new oxygen supply from
outside the cage, a supplementary oxygen supply is
needed; this has traditionally been done by using a series of
perforated hoses, which have to be dragged over the cages
and then lowered onto the cage floors.
Although this is a labour-intensive and time-consuming
process, it does not always deliver optimum distribution of
oxygen. SOLVOX®
DropIn was designed to overcome the
operational and effectiveness issues involved with more
traditional methods of de-lousing.
Application
The most outstanding aspect of the technology is its
method of application; as it was specifically designed to
deliver ease of operation when supplementing oxygen to sea
cages.
Using a small crane, SOLVOX®
DropIn can be easily
lowered to a desired water depth. The oxygenation unit
works by sucking water into the lower part of the unit
and mixing it with oxygen. The oxygenated water is then
distributed throughout the cage through four nozzles situated
at the top. The microbubbles created have a low rising
velocity so extends the bubble residence time in the water.
Combined with the large surface-to-volume ratio, this
increases the efficiency of the oxygen dissolution, even
at low pressures. It has also been observed that this much
less disruptive method of delivering increased oxygen
has resulted in calmer fish behaviour during the delousing
treatment.
The technology is supplied in two delivery options, with
one option featuring SOLVOX®
DropIn as a standalone unit,
and the other comprising of not only just the unit itself but
in conjunction with a “Twin Kit” with additional operational
accessories including starter box, dosing panel, hose and
power cable.
The Twin Kit is ideal for short-term oxygenation and
de-lousing treatment that requires installation and quick
removal, reducing laborious handling, while the standalone
unit makes sense for continuous oxygenation where
repetitive installation and removal of the unit is not required.
What’s Next for DropIn
Since its launch in autumn 2015, SOLVOX®
DropIn has
been very well received by the fish farming market and is
currently in operation in fish farms in Australia and Norway.
During trials, customers provided feedback that SOLVOX®
DropIn operated at high levels of efficiency and they
experienced up to 40 percent less oxygen usage as compared
to existing oxygenation systems utilised. The technology
has also recently won a coveted innovation award at the
Industriens Motemesse show in Norway.
It is expected that the technology will be rolled out to
other key fish farming geographies including New Zealand,
Scotland, Chile and Canada this year. Opening market
potential and providing the world with more protein,
aquaculture will be a growing trend, and SOLVOX®
DropIn
is designed to enable this going into the future.
As with many other areas of industrial gases development,
innovation involving digitalisation and data analysis will be
key. Linde is already well set on course to developing more
intelligent, ‘smart’ technologies in the area of aquaculture
which will serve significantly beneficial to fish farming
operations in terms of productivity.
Linde Innovation Centre for Aquaculture
Linde undertakes the research and development
of all its aquaculture technology at its pioneering
Innovation Centre in Ålesund, Norway. With its highly
equipped laboratories demonstration tanks, the Centre
allows aquaculture technologists to observe how the
latest oxygenation technologies impact farmed fish
development.
Since its opening in 2012 Linde has introduced
the capability to run warm water trials to understand
and assess the performance of its technology in high
temperature water environments inhabited by more
tropical species. Additionally, they have recently
installed an external floating dock where technology
trials – including SOLVOX® DropIn - can be
performed in the surrounding fjord.
Image:
The Solvox
innovation
centre, Norway
FISH FARMING TECHNOLOGY
52 | March | April 2016 - International Aquafeed

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