Some common spawning problems

The eggs dont hatch 

This is common if bettas are spawning for the first time. Inexperienced. Young and passionate to carry on the line. Male maybe too young for spawning.

Male eating up the eggs aka egg eater 

Inexperienced as well. Young bettas need more practice to be familiar in spawning. Same goes to humans right ? You get what i mean..

My bettas just dont spawn 

Not all bettas spawn. Its just like you dont jus like any girl on the street. Same goes to bettas. Many factors such as water parameters, age(be it too young or too old), not having proper food and nutrients. More importantly, its usually the conditioning process being too short. Especially for bettas you just bought home from the aquarium shop or local breeder, they need more time for conditioning. Be patient and not be too rush into things. Allow them time to settle into their new environment.

The pair are fighting vigorously 

You notice after you release the female, she loses quite a bit of her fins, then its time you chimney her again. Make sure you dont lose her due to injuries. Re-condition them again. The longer you condition, the lesser the fight. Let them get used and fall in love with each other.