It would be better for you to put the image in the APUG gallery and ask for feedback. There is actually a critique gallery you could put it in.
I like the image. I like the abstract quality of different elements in space. I personally would rather the leafs in the front were in focus and I would rather you didn't get the sun in the corner. You could probably get the water clearer if you used a polarizing filter.
With regard to the subject, your putting yourself in the tradition of Japanese woodblock printers like Hiroshige. Thought I'd mention that in case you weren't conscious of it. He used to frame a lot more radical than you did, maybe that could be an avenue you could explore along further.
Looks real good to me. I like to see the surface of the water. Don't try to make the water dissapear by making it clearer.
You could try with a polarizer to reduce the reflection and try it different times of day if you really wanted to. Some B&W could turn murkiness into rich tones of gray as well instead of brownish mud.
I would prefer this image pretty much cut in half, horizontally right below the head of the fish, sort of making this koi heading into left bottom corner. I can't explain why but works better for me that way.