All You Need Is One
Collect the Bonus Bubbles first (yellow box), then open the purple seaweed gate. You need to get at least one Jelly to the Krabby Patties. Wait until the Jellyfish room has thinned out a lot, then move Patrick inside to push the box into the position along the white path. You'll need the Jelly to bounce off along the purple arrow (a 50-50 chance). If the Jelly doesn't, it will swim around the level before returning to the same spot for another chance. Hence, while you only need one, the more you can free the quicker you will be able to finish the level.