at 1 inch they're probably 4-6 months old and will likely not develop to sexual maturity for at least a few years. If you want to breed them you have to feed them. My cousin has a clarki in his 125g. it's been in there going on 2 years, and it's only about 1.75" long. This species grows upwards of 6" but in his tank that little clown has been competing with about 15 other fish (mostly damsels) amd 1 very large moray eel. Even with all that competition, the fish seems healthy, but severly stunted in growth. Quality foods in proper quantities will speed maturity. Also the presence or lack of an anenome seems to have a big impact. Just an FYI though on the nem --- They can be very difficult to keep, and can ravage entire colonies of coral. What kind/size system do you have them in?