Thank you! It's great to get some feedback. I agree with the curve. Next to other koi designs he looks a bit stiff. But I'm happy with the scales. As for the water, I sort of butchered the Japanese-style waves. With it's many faults I feel it's strengths make up for it. I learned some things drawing this, so the next time I'm commissioned for a tattoo design I'll do some things different.
I might add a little more curve in it. I worry how it might contrast on the arm. It might end up looking like a straight board but it's something you would have to see on the person. The detail is amazing. I especially like the fin under the water. The water also gives opportunity for some nice pattern.