Oh, great. I get to critique an image by one of the people who keeps DPC on an even keel. And the guy does a fish picture!
Okay, you didn't score well (no kidding) with this rather nice creature which is almost a caricature of a fish. It's well composed in the frame, with good overall balance. Those horizontal swirls behind the fish balance the vertical orientation of the fish perfectly. You must have had a murky fish tank indeed, to be forced to use ISO 1600. Usually you can eke out a bit more ambient light than that in an acquarium shot.
Of course the voters went into a feeding frenzy over all the grain thus produced. That is the only real reason I can find to have this humorous image rated so low when it meets the Challenge nicely and is funny to boot.
Dare I say it? I wish you the best of good luck in future Challenges.