05 June 2024

Roughly 5 times per year, The Deep takes delivery of around 20 tonnes of salt, arriving in bags that weigh 500kg each. This salt is then mixed with tap water behind-the-scenes and subsequently pumped into exhibits throughout the aquarium. Read on to find out more about the process and why we make our own salt water.

Despite The Deep being so close to a large body of water, the Humber estuary experiences large fluctuations in salinity with the changing tides, so cannot supply our exhibits with the levels of sea water required. The Humber receives both sea water from the North Sea basin and fresh water from rivers and tributaries from a catchment of around 20% of England’s land surface.  Both sources also bring an abundance of suspended sediment, giving the estuary its muddy appearance.

Because of this, The Deep’s Husbandry team store tap water instead within large concrete chambers behind-the-scenes, before running it through a Reverse Osmosis filtration system. This forces the water through super-fine filters, leaving crystal-clear, clean water. 1 tonne of salt is then added at a time (2 bags worth) into a 30,000 litre mixing chamber to achieve a salinity of 33 parts dissolved (33ppt) salts per thousand of water (33g salt per 1kg water). From this chamber, clean salt water is then pumped to any exhibit in the building, maintaining optimal water conditions for all the aquatic marine animals. This includes our biggest habitat, Endless Ocean, which contains 87 tonnes of salt alone! For this reason, The Deep uses around 100 tonnes of salt per year.

Instead of discarding these salt bags, we partnered with local waste firm ReFactory, who specialise in creating something new from tricky to recycle plastics. Thanks to their textiles team, our salt bags have been upcycled into useful tote bags, which can be purchased via our online shop and in our Deep-Artment store!

Take a look