They want to play with each other or they are bored and hungry. The third reason is bullying, leave the fish that bully's in a seprate tank for a while until it stops.
The only real way that a parakeet can die if another one doesn't peck at it is through the transmission of diseases.
Cockatiels preen each other. This may appear as though thy are pecking at each other's heads.
There are 2 gallons in one peck.
Well, smart one, it depends on the fish. One fish will eat a different fish than another one.
Well, smart one, it depends on the fish. One fish will eat a different fish than another one.
Eight quarts are in one peck
To the shark - Nothing. The Remora would have to find another big fish to scavenge from.
Well one is a stone fish another is a cone snail. Another is a box jellyfish. Also there is even a venomous shark. That would be the spiny dogfish There are also more fish like the lion fish and scorpion fish.
Peck.Peck.Peck.Peck.
One fish would be a tuna fish.
The coelocanth is one example of a lobe finned fish. Another example would be the six extant (non extinct) species of lungfish.