First, we attach a thread to our plastic fish.  Thread your needle and push it through the top fin of your fish.

Make a loop and tie off the thread at the fish. Cut your thread to about six inches long.  Leave the needle and the fish attached to the thread.

It helps if you have something to rest your ball on so it does not rock.  Here I am using a roll of washi tape.  You can also use a ribbon spool like I do in the video.

Fill your ball with some small gravel.

If you have small seashells you can add them as well.

Next, with your fish still attached to the needle push the needle up through one of the holes in the cap of the ball.

Lower your fish into the ball.  Place the cap on.  Adjust the length of the thread to the height you prefer.

Wrap the thread around the top of the capl until it is secure.

Remove the needle, cut the thread and add a small dab of hot glue to secure the thread to the cap.