The aquarium was closed to the public in 2012 and slated for demolition after it was found to be less than 15% of the new-building standard for earthquake strength.
Since then, the university’s marine science department has struggled to find teaching and lab space.
Since then the project has been expanded in scope, going from a budget of $3.525million to about $5million, and ground conditions have resulted in construction delays.
Chief operating officer Stephen Willis said the project was now due to be completed mid-way through this year.
This comes after independent geotechnical reports found the cliff behind the facility needed more stabilising than expected, delaying the project by about a fortnight, Mr Willis said.
The project was further delayed when the old building was demolished and contractors found it had been built on poor ground conditions and an old watercourse.
This meant extra work had to be done to create foundations meeting modern standards.
Demolishing the 1960s two-storey public aquarium and teaching lab involved dismantling it piece by piece, loading those pieces into a skip, and repeatedly hauling the skip by crane up the cliff behind the building.
It was the smallest of the main buildings on the site. The two neighbouring buildings are still in use.
The ground floor of the new building will contain temperature and light-controlled rooms for research, an area dedicated to dive support, and storage for equipment needed on research vessels.
A 42-seat teaching laboratory will fill the first floor, which will have display tanks for teaching, seawater taps and several ‘touch tanks’ — all resting on a section of specially reinforced floor.
The system for distributing seawater around the site is also to be upgraded, to improve the water quality and to pump 1.4million litres a day instead of 900,000 litres. Two large holding ponds beneath the three-storey lab are also to be refurbished.
They were built in 1903 for a fish hatchery that occupied the site until the university renovated the hatchery to create a marine biological station in the early 1950s.
Cracks in the bottom of the ponds let seawater leak in and out, which could affect research into the food fish eat, because food comes in with the harbour water.