Nothing really prohibits clown knife fish, they tend to swim midlevel with their faces angled downwards to pick off prey. Their dappled markings help them blend in to plants and the big thing to note is that they appreciate company, i've read that they are patriachal (one male to a large group of females) but have never been fortunate enough to test this theory, i have had the pleasure of two of these bests, and occasionlly they would fight like cat and dog!
They are more active at night tho and are really aggressive hunters with a mouth almost as deep as they are (remember they become big and hunch backed)