Fish farm

Fish farm achieves optimal water conditions with Flygt pumps

In the middle of Luneburg Heath, far from any major body of water in northern Germany, Heidefisch GmbH farms rainbow trout and trout caviar. With limited freshwater intake in the area, the company focuses on continuous water circulation and treatment. The concept has proved successful – it was the first aquaculture facility in Germany to achieve Aquaculture Stewardship Council (ASC) certification.

The latest expansion of the business includes a new raceway that will increase production capacity by around 150 tons a year. These demanding fish, farmed without medical additives, need the water to be in constant movement if they are to thrive. This is taken care of by pumps from Xylem’s brand Flygt: they provide a winning solution with high energy efficiency and reliability, and excellent service.

A growing family aquaculture business

Around the turn of the millennium the Winkelmann family made a transition of their own, moving from dairy and arable farming into aquaculture and fish farming instead.

“At first the fish farming was more of a hobby,” says production manager Stephan Winkelmann. “Things have now completely reversed, and it’s the cows and the fields that are the hobby.”

Previously, Heidefisch GmbH had a capacity of around 650 tons of rainbow trout and 50 to 60 tons of trout caviar per year. The new installation increases capacity by 150 tons of fish a year, helping to satisfy high levels of demand. Heidefisch GmbH supplies its delicacies to customers as far afield as Japan – indicative of the high quality of their products.

In the new tank the water flows in a circular movement to offer the fish a habitat with a current, as required by their species. Since this means that the rainbow trout flock together, the facility has been designed for up to 90 kg of fish per cubic meter of water – in other words, around 45 fish per cubic meter.

Ensuring a constant flow rate for water circulation

To keep the facility operating safely, the water must be in constant movement. Heidefisch GmbH chose pumps from the Xylem brand Flygt to do this.

“Their energy efficiency is simply the best,” says Winkelmann. “We compared lots of different pumps and the Flygt pumps achieved the best results. What’s more, they’re reliable, have a long service life, and the service is excellent.”

The Xylem pumps run non-stop behind a drum filter that removes debris from the water. After the initial filtration – a Flygt 3127 impeller pump transports the suspended solids away – the water is separated. One part is carried to the biofilter by a Flygt 4660 propeller pump. In the other direction, two 4660 series pumps transport the water through two cascades for enrichment with oxygen.

A particularly useful feature is the unique maintenance mechanism that allows the pumps to be lifted out of the water on the mounting rod without tools for easy inspection. In addition, the wide-hub design ensures they operate without clogging, which reduces maintenance. And should anything happen, they can be quickly replaced and without great expense – Xylem has a pool of rental equipment (the largest in Europe) that includes all current pumps, so it can respond as quickly as possible.

Careful monitoring of oxygen content during circulation

After the water has fallen through the metal grating of the cascade and been swirled, in the next step three Flygt 7020 series column pumps push the water under an artificial oxygen canopy to a depth of four meters, increasing the oxygen content to 130 percent, before the water is returned into circulation. In the central section of the channel a fourth Flygt 7020 pump swirls the water again.

The water circulates once through the complete cycle in about 25 minutes. The system is controlled via sensors that monitor various aspects, particularly the oxygen content of the water as well as height control for the drum filter, so that water can constantly be fed to the biofilter.

Winkelmann was able to test the new setup using test equipment provided by Xylem. In doing so, it became clear that the heat added by the submersible pumps is not a factor. On the contrary, the heat is clearly outweighed by the benefits of this space-saving installation and compact system with few moving parts.

“The pumps are part of the whole concept, so it was extremely important to choose the right solution,” says Winkelmann. “Xylem supported us right from the start. We’re now putting it into operation, and we’re completely satisfied.”