The National Aquarium, Washington D.C. will close this September. The original timeline for opening the new aquarium at the other end of the Hoover building is no longer relevant. I'm not sure if there are still plans to have the aquarium on the Mall side of the Herbert Hoover Building or not. The aquarium will be closed permanently until funding and a new location is found.
National Aquarium in D.C. to Close September 30: DCist
I missed that this facility was closing. Didn't they just rebuild the whole facility? Most reviews of the place weren't very glowing so maybe not a huge loss? The National Zoo has a pretty nice little aquarium with octopus, nautilus, etc. in its invertebrate exhibit.