The Tennessee Aquarium in Chattanooga celebrates its 20th anniversary on Saturday by opening a big-in-more-ways-than-one exhibit, “River Giants.”

It will be populated by what curator of fishes Thom Demas calls “Goliaths of freshwater,” including giant pangasius catfish that can reach more than 9 feet and a 7-foot beluga sturgeon.

Demas said species including marbled eels, ghostly alligator gar and wallago catfish will add an element of the weird to this new collection. He called the wallago a personal favorite: “It has the face of a bullhead and an eel-like body. In Southeast Asia, wallago can grow to eight feet.”

Zeb Hogan of the National Geographic Channel show “Monster Fish” will appear at the exhibit opening, too. “It’s pretty easy to love, and to be curious about, these fish,” Hogan said. “They are really hard to find in the wild and most of them occur in very remote parts of the world.”

Check out this video of the "River Giants" exhibit construction, compressing a month of work into 2.5 minutes:
www.youtube.com/watch?v=9kTHm95_VJI&list=UUfjM_SYJjO_UbMKaake95aw&index=1&feature=plcp

Also on Saturday, the Chattanooga River Market will fill the Aquarium Plaza with art and crafts and other locally produced items, with street performers and live music adding to the scene during the day. And, for the first time, the River Market will hold extended hours into the night.

The Aquarium’s free “Party by the Peaks,” starting at 7 p.m. Saturday, will feature a performance by the world music outfit OGYA.

Aquarium admission: $24.95 adults, $14.95 ages 3-12. 1-800-262-0695, www.tnaqua.org.