The National Aquarium's massive, $12.5 million new permanent coral reef exhibition, "Blacktip Reef," was slated to open July 10 with more than 1,000 animals of 75 different species -- including 20 blacktip reef sharks --  lurking within its 260,000-gallon tank. When complete, visitors would be able to gaze upon an aquatic universe that swirls around a meticulously created coral reef.

But the Aquarium announced today that it's going to take longer than expected to realize that vision.  "We’ve decided to give the 1,200 residents of Blacktip Reef more time to acclimate to their new home," National Aquarium CEO John Racanelli wrote in a statement. What it means is that the Aquarium will now add the animals in phases over the month of July, even as the exhibit opens to guests.

The National Aquarium's $12.5 million "Blacktip Reef" exhibition won't have sharks by opening day. (National Aquarium photo)

The Aquarium had planned to introduce more the animals, including a 500-pound green sea turtle named Calypso and 20 blacktip reef sharks, to the tank by the last week of June. Under the new schedule, Calypso will be introduced tomorrow along with several other species, and the sharks will go in sometime in late July.  Visitors over the next few weeks can make their way through the exhibition space, and see the animals as they're added to the growing ecosystem.

Read more: The Summer Bucket List