Hey buddy, I think that, Flower Horns need time to "GET TO KNOW" the aquarium and the environment. My Flower Horn also behave like this when I 1st bring this tiny little feller(about 2 inchs) back to my house and put it into a 4ft aquarium.

This little feller keep hiding at back of the pump, and some conners that grown up with some algeas, pretending to be algea. LOL

And i feed him 3 times a day with Red Worms and pallets. And now i'm trying to train this feller, and i think he is getting used to the aquarium and sometimes chase my fingers when i put them on the glass. And i keep some small fish with it, and this feller keep chasing those other small fish! What a mean fish...Interesting!

Regards,
John