Clowns do not start spawning until they are at least a few years old. Look online for more detailed instructions, but basic protocol is to have the pair in a bare tank with a clay pot, feed several times a day with varied foods such as otohime pellets and fresh seafood, then wait until they spawn. Once they spawn, remove the pot with eggs a day prior to hatching and put them in a bare larval tank. They'll hatch at night and will take live rotifers, then several days later live baby brine can be mixed in. Daily 50% water changes will take care of ammonia. After 6 or so days they can start to be weaned onto dry foods, then after meta they can be moved to grow out tanks. It's not the most complicated process ever, but it does take dedicated tanks and a lot of time and effort. They're not like guppies; you can't just collect the babies and put them in a plastic breeder box.
In terms of killing babies, you won't be. They won't breed for at least a couple years from now (in some cases almost a decade) and when they do, the other tank inhabitants will enjoy the nutritious snack. And keep in mind, the goal of reproduction is to have just 2 babies make it to adulthood to replace the parents. All the others are meant to be food, so if they get eaten, they're just doing what they were made to do.
