At Disney’s Aulani Resort &Spa at Koolina, the colorful reef fish in Oahu’s only human-made snorkeling lagoon are doing more than just swimming about looking pretty for the hotel’s guests.

They are contributing to science.

The Aulani aquarium program is working with the Oceanic Institute of Hawaii Pacific University to help in the breeding of reef fish that historically have had only limited success in captive reproduction.

“Their efforts to collect eggs have significantly improved our ability to conduct hatchery research on some key species,” said aquatic researcher Chad Callan, director of Oceanic Institute’s finfish program.

In fact, eggs collected from the Aulani’s Rainbow Reef snorkeling lagoon since 2016 have resulted in the first-ever successful captive breeding in Callan’s lab of the milletseed butterflyfish, potters angelfish, Hawaiian cleaner wrasse, yellowtail coris and yellow longnose butterflyfish.

Callan said the Aulani eggs have allowed his lab to test its culturing methods on more reef species, to see how broadly applicable they are.

“So far, it’s been a really great partnership and we’re really excited to see it continuing to grow,” he said, adding that he’s working with other aquariums in the state as well.

At the Aulani, officials are aiming to have an impact on the sustainability of their reef species and the global aquarium industry, including the potential to lessen the number of fish taken off reefs around the world.

Rainbow Reef is a 166,000-gallon aquarium stocked with 1,000 reef fish, almost all of them Hawaiian species.​ With a solid diet and highly filtered water, the lagoon is an idyllic, stress-free environment with no predators.

The finned cast members earn their keep by sharing their space with snorkeling hotel guests from 10 a.m. and 3 p.m. daily.

For the last few years, the resort’s aquatics team has been collecting millions of fish eggs from the lagoon — including an incredible 200,000 in one night — and made them available to Callan’s lab in Waimanalo.

For the past year or so, Aulani senior aquarist Eric Curtis has logged a description of the eggs, complete with hand-drawn sketches of each type he can distinguish using a microscope. Viable eggs are then transported to Oceanic Institute.

In the wild, less than 1% of the eggs produced by fish end up as an adult.

At Rainbow Reef, the eggs that survive any hungry fish float to the water’s edge, where they are captured in filter socks that are placed in the lagoon’s skimmers situated all around the lagoon.

“We don’t know what type of eggs we’re going to get,” Curtis said in a recent interview. “It’s really cool. It’s almost like Christmas. You don’t know what you’re going to get, and all of a sudden it’s what shows up.”

Curtis said he’s working to identify the egg type and peak spawning periods of various species. Most of the spawning, he said, takes place in the summertime, but it’s happening all year long.

A former fish disease specialist at the Waikiki Aquarium, Curtis was hired by Disney even before the Aulani was built in 2011.

“I was here from the beginning — even before the beginning, when the fish were quarantined off site,” he said.

Today, Curtis is proud of the healthy Rainbow Reef community he helped to create. It includes fish species selected with compatibility in mind and lots of herbivores that are busy eating the algae that grows naturally in the Hawaiian sun.

“It’s a complex formula,” he said of the ingredients that go into keeping the lagoon and the fish happy and healthy. “There’s an art to it.”

Raffy Jacinto, animal and water sciences operations manager at Aulani Resort, said the successful egg collecting project is a reflection of the overall health of the residents of Rainbow Reef.

“If they’re comfortable enough to mate and not worry about survival, that’s a good thing,” he said.

Curtis said one of the goals at the Aulani is to teach people how to treat the reef.

“The nice thing about this is that 24 hours, 7 days a week, you’re going to have clean water with good visibility, versus out there you don’t know,” he said, pointing to the ocean. “This is a good intro to Hawaiian fish and snorkeling.”