Sometimes it will retract, specially if the light is dimming for the night. Let it be and see how it does tomorrow. Normal behavior [emoji6]
But for the heck of it:
What are your Parameters? Ammonia, Nitrate all zero
Lights? LED that comes with biocube
Flow? medium
Any recent changes? Did a water change this evening took out and put in about 7 gallons. It was fine after the change. Although all lights are out it has come back out a little. I think that you are correct . It may simply be something that it is doing since the blue lights came on.
Wall hammers are very sensitive to change in the water. Just a heads up for future reference.
-Zack, who thinks its normal.