Some aros (specially small ones) takes longer time to adjust to its new environment. Just make sure your water is in good condition and it should be ok. Aros adjust faster to a smaller tank so you can put a divider to make it look smaller for the aro, or you can make the water level lower. TAnk mates, higher temp, lights off will help a lot. Others go to the extent even of covering the fish tank so that the aro wouldn't be jumpy specially if the tank is on a high traffic location.