The latest instalment in Josh and Julie Niland's rapidly expanding Sydney seafood empire, Fish Butchery Waterloo, launches on Thursday.

The slow creep inland is a first for the eastern-suburbs based group, and the new venue has some tricks up its sleeve.

The hatted chef is excited about his new kit and the flexibility of the Bourke Street space, previously Lotus Hunan Chinese Restaurant, which is twice the size of the Paddington original.

Josh Niland says they'll add an eat-in option, hopefully in early March.

"Eating charcuterie from the fridge is something we haven't been able to offer customers at [the original Fish Butchery] in Paddington. We're excited to do it," he says.

With the upmarket Saint Peter restaurant and Charcoal Fish already in their arsenal, the duo's fourth venue provides a blank canvas to push hard on design.

Floor-to-ceiling windows offer passersby a glimpse of the butchers trimming and cutting seafood to order at the 13-metre marble counter.

Fish Butchery Waterloo will act as the central processing kitchen for the hospitality group, as well as somewhere to buy fresh fish and the Nilands' cooked specials.

Yellowfin tuna cheeseburger is on the opening menu in single, double or triple options, as is Murray cod souvlaki straight from the "vertical" kebab cooker, and a tuna meat pie.

Dive into the freezer for take-home Aquna Murray cod fish fingers or yellowfin tuna lasagna.

"Our mission at Fish Butchery is to work with remarkable fish caught and handled by extraordinary fishers that care about the details as much as we do," Niland says.

"If we insist on continuing to consume only half the fish, there will be no fish left in years to come, regardless of how sustainable they are. The issue of fish wastage should not be in the hands of the consumer; it is in the hands of those who catch, prepare and sell … The idea is to utilise fewer varieties of fish but use the species in its entirety."

Open Wed-Sat 10am-7pm, Sun 10am-6pm.

965 Bourke Street, Waterloo, fishbutchery.com.au