The ratio male/female can be influenced. It's not a quarantee but it is most likely that it will work.
With most livebearers (so, not all..) if you start increasing the water temperature more during the whole pregnancy of a female (so, not at a later stage!), the chance that more male offspring will be born is higher. Water temperature between 26°C (78,8°F) and 28°C (82,4°F) during pregnancy.
Devoted aquarist ever since early 1970's...
Specialized in livebearers &
specific breeder of rare livebearers...