it's cool, they are just being shy at that size. my "O's" did that all the time. Let them get to know the 55gal and start a patten with your lights. turn your light on in the morning and turn them off at night. is the tank in a bed room? living room? if in a bed room, at night when you turn off the tank lights, keep a soft night light on in your room...so that you not shocking them when you turn on the room light.