They are pretty shy with people around.
It is good to know you saw them active in the "dark". Mine hide almost all day and just dart out periodically and when I feed mainly.
They are maybe hungry. Maybe feed right as you are shutting down the lights for the night. Say like turn off their tank light but leave a light on in the room and feed them then. They can get really long. Mine have been in a tank with larger fish than their mouths. They are bug (meat) eaters and would like live food and worms.