BALTIMORE — The National Aquarium in Baltimore has overhauled what once was a drab, leaky, concrete tank of mostly sting rays, adding 1,000 animals and 3,000 hand-sculpted coral replicas to create a colorful and massive new centerpiece exhibit.

The massive central tank had always been popular but became dated, and it is now teeming with new life after the $12.5 million renovation. It now includes 65 different animal species, including a beloved 555-pound, three-legged green sea turtle named Calypso.

This week, the aquarium added 20 new blacktip reef sharks from Australia to help complete an ecosystem that replicates endangered Indo-Pacific reefs. Divers carefully placed each shark in the 260,000-gallon exhibit one by one over several hours Monday and Tuesday. Almost immediately, the sharks began swimming together as a school in their new home.

Rather than eat all of the exhibit’s smaller fish, however, these sharks have been trained over the past year to eat a variety of seafoods from animal keepers on schedules and at certain feeding locations, said senior aquarist Ashleigh Clews. The sharks look small now but will eventually grow to about 6 feet long.