The Comet fish(Calloplesiops altivelis) is also known as the Marine Betta because of their similarity to the Siamese Fighter. They are stunning looking fishes that are rarely seen in the open during the day in the wild. The images do not really do them justice.
As one might expect from a fish nicknamed the Marine Betta, the Comet fish has large fins which surround the body from the gill plates backwards. The blue spotted pelvic fins are long and are usually held backwards onto the anal fin which touches onto the oval shaped caudal fin.
The dorsal fin is also large and curves backwards onto the caudal fin. When swimming, the fins are kept erect but in a confined space the fins are folded down. On the rear of the dorsal fin there is a large black eye spot surrounded by a white line. On the upper front of the caudal fin in the caudal area is a yellow mark and there is a corresponding smaller yellow mark on the lower front section of the caudal fin which is not as prominent.
The juveniles seem to be a darker black color than the adults and have less spots on them. As they age the spots become proportionally smaller and develop into lines running horizontally across the body and radiating out on the fins. The dorsal and anal fins develop a light brown color with age and the rear of the caudal fin goes white.
IN THE WILD
The Comet fish is a reclusive fish usually seen at the entrance to a small hole into which they will retreat at the sight of a diver. Often they leave their tail sticking out the hole and this is said to mimic the head of the White-mouth moray eel (Gymnothorax Meleagris).
Whether there is any substance to this is hard to say and one can draw ones own conclusion as to whether there is any resemblance between the two by comparing the image below with the images of the White-mouth moray. Personally I am sceptical because they seldom leave the tail sticking out for long in my experience.
If one stays in front of the hole the Comet fish will usually come out to inspect you while staying close to its hole. If one stays for long enough they gain confidence and will come right out and display. This can be seen in the images.
Sudden movements and blowing air out quickly cause them to head back into the hole, but if one moves very slowly and releases air carefully they go from being reclusive to down right curious.
The main diet of the Comet fish are small fish and crustaceans. They feed at night and swim sideways up to their potential prey trapping them. With their eyes being black and very difficult to distinguish, as can be seen in the image below, the prey often assume the yellow eye spot is the eye and try and escape past what they assume is the back of the fish making them easy for the Comet fish to capture.
While they resemble the Siamese Fighter in looks, they have another similarity in that the males also look after the eggs. Because they have been bred in captivity we know a little but not all about their mating behaviour. The male and female go into a hole together and the eggs are laid in the cave and are then cared for by the male.
The Comet fish being a very attractive looking fish is kept in aquariums. They have a reputation for being tough and fairly easy to keep and have been known to live in a tank for up to eight years. They may be difficult to transition off live food. Being slow movers they will not be able to feed with more aggressive fish in the tank.