I was able to quickly assembly a skeleton using the Joints tool in Maya and animate the Koi. I did this several months ago and it took me much longer. Again, iterations/repetition really helps you become more proficient and become faster each time. He animates wonderfully in Maya, with a cute little wiggle in his tail.
I watched a few Youtube tutorials on how to Bake the animation and export as FBX, then import into Unreal. As you can see in my Contents folder, the model imported with an animation, skeleton, mesh, etc. When I double-click on the animation, it animates beautifully in the editor dialog box. Unfortunately the Koi does NOT animate when I play the scene. Need help troubleshooting this.
I tried to animate directly Unreal using the Sequencer tool, which seems to animate fine when you play it inside the editor, but again, there is no animation in the actual game. Need to research more on animation.