Step 15: Darken the path of the triangle-like shape at the bottom for the Moorish idol's anal fin but make it wavier. Draw the right side of the fin as a continuous wavy line that meets the tail.
Step 16: To the left, draw two long, curved lines that come to a point for the Moorish idol's first pelvic fin. The two lines bulge outward in the middle before becoming narrow at the bottom.
Step 17: Darken the bottom edge of the initial circle. Draw the fish's pelvic fin on the other side the same way as the first. Darken the lower, left edge of the initial circle to finish the bottom part of the Moorish idol's body. Darken the top, right side too but make the line bulge out a bit over the eye.
Step 18: Use the remaining lines on the right as guides to draw the Moorish idol's caudal fin or tail. Follow the basic path of the guides but make the shape wavier as you darken the lines.
Step 19: For a cleaner look, erase as much as you can of the initial guide lines. Don't worry about erasing all of the guides. It's okay to leave some behind. You can also lightly erase some of the final lines so that the colors don't get too muddled with the graphite in the next step. Re-draw any final sketch lines you may have accidentally erased.
Final Step: Color your Moorish idol drawing! Use black to outline the stripes on the body. These fish have a big, fat stripe in front of their bodies, a thinner stripe in the back and a black tail. The thick stripe at the front also has two thin white lines. You can skip these lines because they're not too prominent. Add a V-shaped line to the top part of the fish's mouth and start filling in the stripes with black. Add the color lightly at first and slowly build up to the level of darkness you want.
Color the Moorish idol's eye and the portion of the pectoral fin in front of the stripe lighter. The pectoral fin is transparent. To get this effect, just follow the path of the stripe and color the fin lightly. Coloring the black stripes can be a slow process, so be patient and take breaks.
Use yellow to color the right side of the Moorish idol's body. Add a bit of yellow to the right edge of the pectoral fin to emphasize its transparency. Be careful as you add yellow to the fish's body as it's very easy for it to be muddled up with black. Add a bit of black along the right edge of the body. Use yellow-orange for the section on the mouth. Blend in some yellow- orange to the yellow on the body as well.
Use gray at the bottom of the Moorish idol's body as shadow to give the figure more dimension and volume. Use different shades of gray or vary the pressure on your pencil for different degrees of tonal value. Add a few lines to the dorsal fin for the folds. It's always a good idea to use reference for a more accurate drawing. Add a bit of purple to the shadows. Don't forget to pause the video to draw at your own pace.