I have a male H. kallochroma in my tank for more than 8 months. It is said the female and juvenile have a spot near the tail, while the adult male does not, and the color is brighter for the latter.
The fish usually swims near the bottom with rapid speed during daytime, through the corals. it eats every kind of food, including most of zoogenic foods and dry green algae.
The H. kallochroma needs deep sand bed (5-10cm at least) at night, drilling into the sand to rest when the light fades out.
It is always peaceful to other fishes.