Wow, It's amazing, man. But it's not a secret, that in the ocean the biggest creatures remains alive. But there are situations, when not very big creature can kill all the big fish. I'm taking about the worms (bristle worms), that can be as evil ones and as save ones (depends on their type). Frankly speaking, I haven't ever seen them in the real life, but the videos in the Internet make me be afraid of them (I am the owner of the fish tank, so there is always possibility, that one day I'll find such creature in my aquarium) and the other creatures, that can kill my fish. So, take care of your fish, guys.