There is a type of jellyfish I know of that only exists in the tens of thousands in only one volcanic lake in the world because they only require water and sunlight to survive, and there's no predators there. They lack any defeces because they have no stinging cells. Sadly I can't recall the name...I think they'd be cool.
Also...a hive of Japanese bees, they hardly ever sting and kill other insects by crowding around it and generating heat. They can take the heat very well. You can even handle them without safety equipment or smoke due to the fact that they're so docile.