Add a cylinder (Shift+A, mesh cylinder) at the end of the fish body, near the tail. Adjust the position of the cylinder so that it fits the width of ...
The koi fish symbolizes a bunch of good things (strength, prosperity, good luck, yadda yadda) in some Asian cultures, and a gold colored koi specifically symbolizes wealth and prosperity. With or without money, whipping out this clip from your pocket allows you to keep it classy while taking a fish out of your pants.
Step 1: Make fish outline
Find a picture of an uncontorted koi fish online. Put this picture in the background of the 3D viewer on Blender. Add a plane, delete three of the points on the plane, and extrude the point (Ctrl + LMB) as many times as needed to draw the outline of the fish. Close the fish outline by selecting the first and last points only and connecting them (F).