What size do oscars have to be before they start breeding, i.e. pairing up and laying eggs? Please say if the size includes or excludes the tail

It's best to go by age rather than size. Oscars will be sexually mature from a year onwards. My breeding pair didn't start until they were around 14 -15 months old. They could be between 8 inches and 10 inches

I mention this somewhere on the website. Freshwater fish should be measured from their nose to the tip of their tail. Measuring fish in salt water can sometimes be slightly different.

Ok cheers for that. I mentioned about the tail thing because some people include the tail and some dont. Will include the tail from now on