Goodnight, Moon. Goodnight, Fish.

A trip to the aquarium no longer means neat lines of grade-schoolers led past murky fish tanks, all the while being admonished to keep their noses off the glass. At the Long Beach Aquarium of the Pacific, a popular program has kids sleeping with the fishes--in the non-”Godfather” sense of the phrase.

“Lifestyles of the Fish and Famous,” “The Reef That Never Sleeps” and “Predator, Prey and Pajamas” are variations on the sleepover theme. All share the same basic elements: Children, along with parents and teachers or Scout leaders, come with their sleeping bags to spend a night at the aquarium.

The sleepover program, which began in 1998, has steadily grown in popularity. Last year, the aquarium offered 80 sleepovers; this year it’ll have nearly 100. Aquarium director of education Amy Coppenger explains the appeal: “At nighttime, the exhibits come alive and the habitats look like a moonlit ocean.”

On a recent evening, the children and parents of a fifth-grade class from Ellwood Elementary School in Goleta were greeted by aquarium educators Gretchen Bazela, Alyssa Edwards and Sunshine Thomas, who set the tone for the evening. The children sat cross-legged under an 88-foot-long model of a blue whale suspended from the ceiling of the grand hall.

“Does anyone know the name of this animal?” asked Bazela, pointing to the underbelly of the beast. “It’s a whale!” the children shouted. She described the dorsal fin, then made a pointed “fin” of her hands atop her head, which became the signal for vertebrates throughout the evening. A call-and-response system got kids’ attention, too: After learning the difference between a predator and its prey, when the educators wanted quiet, they called out, “Predator!”

“Prey!” the kids hollered back, but then got ready to listen.

The average sleepover has about 45 participants, including children and parents and guardians. Fifth-grader Justine Haight said, “I would think you’d have to be in the fourth or fifth grade, so you’d understand about the fish,” but programs are open to kids as young as 5.

Young ones could get restless or possibly frightened, but Coppenger said, “We’ve never had a youngster that didn’t come to enjoy the experience with the fish.”

Parents such as Terre Lapman enjoyed the process of discovery as much as their children. “If you don’t believe in God, you will after you see this animal,” she said, pointing to the Phycodurus eques or the leafy sea dragon, tucked into a small corner tank. The creature looks like the bent spokes of a wheel of twigs--each tipped with fluttering, spotted green “leaves” that camouflage this exotic species of sea horse.

On the terrace, at a waist-high ray tank, Edwards demonstrated a special two-finger technique for touching the rays. They feel slimy, the educator warned the kids, but added, “Slime protects them from bacteria and germs.”

Some squealed, “Eeew!”--but almost all reached into the shallow pool. “I like the sting rays. I have a favorite one--that black one over there,” 10-year-old Taylor Gardiner gushed as she leaned in, stretching her fingertips to just graze the sleek bat ray.

Everyone had a favorite. “The penguins--they’re so energetic. They’re so playful,” said 10-year-old Robert Emmens. Classmate Nicole Eisenbeisz insisted that the jelly room is the best: “The jellyfish are flowing and they’re so graceful.”

The unprecedented access to the exhibits, coupled with the entertaining and informative sessions with educators, fueled lively conversations.

At dinnertime, pizza and drinks were gobbled up at an outdoor amphitheater overlooking the seal and otter habitat.

Then it was on to the 350,000-gallon Tropical Reef, where 2,000 fish--some 200 species, from the blue wrasse to the zebra sharks--swim around a colorful coral reef. An aquarium diver in a wet suit and equipped with a microphone entertained questions from the kids: What’s your favorite fish? Have you ever been bitten? Can you do a back flip in the water?

After games, sing-alongs, crafts and a snack break, the kids selected a campsite--either the Tropical Reef or the sea otter habitat. They would reconvene in the morning for breakfast with the otters and sea lions, who get up early for their breakfast too and make a lot of noise.

Everyone, including the parents, was ready to turn in. As quiet conversations died down to whispers, most sank into an especially relaxed rest. The soft murmur of water circulating in the tanks and the cool blue lighting made it easy to surrender to sleep and dreams of the fishes.

Sleepover at the Aquarium of the Pacific, 100 Aquarium Way, Long Beach. $50 per person; for ages 5 and older. Tuesdays, Thursdays and two Fridays a month. Preregistration required: (562) 951-1630 or (888) 826-7257.