rhodes_96;4278899; said:Darkness wouldn't do that. Try putting something in the tank like some driftwood with plants on it or piece of round pvc piping big enough the fish can hid in. if the fish goes for cover and hides there, and your water parameters are all good, then might just have a shy fish.
Another idea you can try is by lowering the water level in the tank by about half, and see if their is a change in behaviour.
Does the fish constantly face away from the front of the tank ?
I am not encouraging for the fish to hide so i am definitely not providing a place for him to hide lol .... it is very unseeming for an aro to hide. The water parameters are good - he is now the sole (well +bichir) resident of the tank.
For this set-up lowering the water can not be done because of the filter arrangement .... on the side