If you’ve ever spent time gazing into the Living Coral exhibit across from the little blue penguin exhibit, you’ve likely stared into the eyes — or mouths — of the Banggai cardinalfish. These fetching black-and-white striped tropical fish hover together in the water column close to the glass making them very easy pickings for photographers.

Banggai cardinalfish in the Living Coral exhibit
An adult Banggai cardinalfish

Not only are these fish quite photogenic, they also exhibit some pretty interesting parenting behaviors. Specifically, they are mouth brooders. The males of this species have a large oral cavity to accommodate the eggs and young, which they carry around for four to five weeks — safe from foraging reef neighbors. Look closely and you may see him roll the pinkish eggs to rearrange and oxygenate them. Once the eggs have hatched, you may even see some tiny eyes peeking out when the male stretches his mouth. Once the fry outgrow dad’s mouth, they are on their own, and these snack-sized young usually become part of the food chain.

But several months ago, aquarist Brianne Dent managed to collect a brood of babies and removed them to their own floating enclosure behind the scenes. The babies get plenty to eat and — even better — are not eaten!

brianne with banggaie
Time for a tank cleaning! Brianne moves the youngsters into a holding container so she can clean their tank.
aquarist points to baby fish smaller than her fingernail
About a month old, they look just like their parents — only tiny!
baby banggai cardinalfish under the blue UV lights
Baby Banggais under the blue lights

In addition to the fish being very adorable, this achievement is reason to celebrate because wild populations of this species are not in great shape. Banggai cardinalfish are endemic to a few islands in Indonesia (the Banggai islands, of course). It is a challenge to maintain the population in the wild while meeting the demand for the fish at public aquariums and in the hobby trade because they are such a popular aquarium fish. In fact, this species just got listed as threatened under the Endangered Species Act, and the ICUN red list has them listed as endangered. When we are able to grow them in captivity it takes the strain off wild populations.  

It will take up to a year before these tiny fish are on exhibit. First they must grow on their diet of mysid shrimp and other miniature delicacies. But be sure to look for their parents in the Living Coral exhibit. Pay close attention to their mouths, you might just see the next generation of Banggai cardinalfish incubating in dad’s mouth!