In my experience with Spiny Eels (2 Peacock Eels and a Zig Zag Eel), I've noticed that they only really jump when they have something they would have trouble swallowing normally, like say a larger earthworm. So what they do is jump and whip their head down to try and break the food (whatever it is) in half so it is more manageable. Can anyone else relate to this? Let me know if you do.