Well, or so it seemed.

I discovered this last night while I was sort of playing with my flowerhorn. He's about 12 inches long including the tail. As usual I will just move my finger in front of the tank and he will chases it around. But all of a sudden, last night when I kept my finger very still in front of it, the dorsal fin sort of retracted and darker stripes appear within seconds ....very intense dark stripe. He just stays very still as if in trance. But the moment I move my finger away, he's back to normal, the stripes faded almost immediately.

I don't know what strain of flowerhorn I have, but he's always got the stripes, just not as intense. What is happening here??? Is he sick or is it just normal??? This is my first flowerhorn so I really have no idea what is the normal behaviour for them.

Anyone who had had the same experience please do drop a few words here.