I have 6 ITs ranging from 6-9". Only two small ones will stabilize and swim around in the evening. The rest and most the time the two small ones stay dark and hide in the back. Could it be water parameters? I have them with red bay snooks which do not mess with them and stingrays. For the longest time I thought the stingrays stessed them out. The biggest ray in with them is 9" but the little ones come out and at feeding time they all come out but then go back to hiding. I have had 5 of the dats for over 2 years and the biggest one about 6 months. The nitrates stay around 40-60 ppm, could that be it, could it be lighting, I am not sure.