Two-Fin Flashlight Fish (Expert Only)
The Two-Fin Flashlight Fish, also known as the Splitfin or Lantern Fish, features a black body with blue-hued dorsal and caudal fins. It has a distinctive glowing appearance due to bioluminescent bacteria living in light organs located just below each eye.
The glow is typically white but can vary to blue or yellow depending on the fish’s condition or environment. The fish can rotate its light organ within the eye socket to turn the light on or off. This ability is used for communication—such as blinking at higher frequencies to signal to other fish—and for defensive purposes, where it turns on the light to startle predators.
| Key Features |
|---|
| Body Color: Black |
| Fins: Blue dorsal and caudal |
| Light Organ: Located below each eye |
| Glow Color: White, blue, or yellow |
| Behavior: Communicates via blinking, uses light for defense |
FAQ
How does the bioluminescence work in the Two-Fin Flashlight Fish?
The bioluminescence is caused by symbiotic bacteria living in the fish’s light organs. These bacteria naturally produce light, which can vary in color from white to blue or yellow depending on the fish’s health and environment.
Can the light organ be turned off or on at will?
Yes, the fish can rotate its light organ within the socket to control whether the light is on or off, allowing it to blink or turn the light on for communication or defense.
Is this fish suitable for beginner aquariums?
No, this species is classified as expert only due to specific water conditions, tank size, and tank mates requirements. It requires a well-established, mature aquarium with stable parameters.

Emily Nolan –
The flashlight fish is a fascinating addition to my reef tank. The glow is subtle but noticeable, especially at night. I’ve seen it blink in response to other fish, which is a great way to observe natural behavior. It’s not aggressive and stays in the mid-level zone. Requires a stable setup, but worth the effort.
Frank Berry –
The bioluminescence is beautiful and adds a unique visual element. I’ve noticed the fish changes the glow color slightly depending on the lighting. It’s active during the evening hours and seems to respond to movement in the tank.
Jack Ogden –
After several months, the fish has become a regular part of the tank’s activity. The blinking behavior is natural and entertaining. I appreciate the peaceful, low-impact presence. Only recommend for experienced aquarists with proper water conditions.