Re: Fighting to the point of bleeding??
Don't use coconut fibre or hair for birds. It can wrap around their feet and legs and cause the appendage to die and fall off.
Green grasses (between 8-16 inches long) are the best thing for nesting materials. The birds can pick them up and weave them into a nest. The grasses will dry out and are safe for babies and adults.
Can you make your cage longer?
Increasing the length of the cage can make a huge difference to the birds. Even if you only increase the length by a couple of meters it can make a huge difference to how they behave. People tend to forget that birds naturally have the entire outdoors to fly around in and when the birds are confined to small cages, they stress out.
Bigger aviaries allow for landscaping (plants), which can provide nesting areas and hiding places for birds being victimised by other birds in the cage.