Let's see growth of betta fish together.
But these pictures cannot use as standard because some blood or colors has a bit quickly growing rate or a bit slowly growing rate than these pictures.
After they hatch from eggs...
When they are 3 - 10 days old , I feed them by...
disperse chicken red egg in water
When they are 10 days old , brine shrimp or water flea is the best food for them.
More details about raising baby betta fish , please follow this link : RAISING BETTA FISH
All pictures come from : www.bettanetwork.com