Hey! I'm not Nick, but I'd suggest that to try to shade using the complementary colour (blue-ish), in this case, a blue one. In any case, shading in this way will help you achieve certain gray tones, which you can complement by using the brown you mentioned. I'm not an expert in traditional techniques... But I've seen some people do that. Or you can use brown to maintain similar colors. But try to follow the shape of the fish when shading. In other words, think in terms of spheres or cylinders. Hope this helps :) | Artwod Feedback