Matted Filefish Nocturnal?

[FollyFish]

Three dyas ago I got a Matted Filefish to help with an aplaisa takeover. But so far all she had done is sit in the back corner under the heater. I feed when the “night” blue lights come on and she is a little more active then. Im not sure if its because of the food, the lack of water flow (I turn off the powerheads and filter to spot feed) or becuse she may be nocturnal and that is why I see no movement durning the day lights. 

 

There is no aggression from the other inhabitants. Im not even sure if they have noticed the new fish.

 

Does anyone else have a filefish and can tell me about their normal behaviour? 

[Pcon]

I had one until recently, Big mature Female, fell asleep next to the wave pump during low tide. Was always out and zooming pecking for food during the day, slept like a rock during the night. 
Now at the shop I work at there is a file fish in a 180g never see it during the day, but when i come in before the lights go out or I come in to take care of something after hours, I often see it out in the open. Also this tank is very lightly stocked, there is only a lawnmower blenny and a single purple firefish. 

Filefish are relatively shy mine hid for its first week or two in quarantine. I wouldn't be too concerned if she is eating well.