First, if you aren't already, use shortcuts, I found out about them when i was halfway through the game.
Second, if there are beginning to appear more then about 12 or so, do not count them, just when there are a bit too much to handle, eat them in beast mode, then quickly turn back to energy form. Oh and I don't know if you already have someone following you, but if you do, try to stay in beast mode and survive while the other kills the jellyfish, even though this takes ALOT of time, patience and skills, seeing those lasers are hard to avoid with the small critters aroudn you too.