1. How do you sex them?
2. How do you breed them?

I have two koi that were given to my by my grandpa that he picked up at a flower store place..thingy lol. They are a good 3-5 inches atm. One is yellow with silver and a spec of black..and the other is a rainbow and has black,blue,silver,white,and a spec of orange. so.. any info anyone would give me is much appreciated