The Lone Jelly
Since Jellyfish will randomly select to travel either left or right when they hit a wall, you can successfully get the Jelly to the Krabby Pattie along several possible paths. If you don't want to leave it up to luck, the following is a surefire way:
Do not collect the Bonus Bubbles yet. Push all boxes into position along white arrows. Wait until the Jellyfish is at the yellow "X", then open the purple seaweed gate. Once the Jellyfish has passed the corner with the Bonus Bubbles, they are safe to collect.