Perhaps when the bigger ones are all up at the top sucking up the food take a big net to scoop them up. Take them out of there.
Free up the space as you already found there will be a bunch more. Keep up on water changes as those little guys really can foul up the water with feedings and just there are so many.
Your tank 64 liter is appx. 16G, not very big for tons of fry.
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?
Start here - Aquarium Advice Article
FW Favorites right now Clown Loaches, any shrimp - SW Vase Red Mangroves