Ok yes the only way to sex them 100% is to vent them but there are many little indercaters with them
First the males will have egg spots some females may get some but not usually
Second males will get a white / bluey blaze on the anal fin that will almost glow when showing off
Third the males will have a pointed anal fin were the females will have a more rounded one
Fourthly the males will have a deeper body weres the females will be a bit more compact and cylindery
Also lastly the females jaw/throught can be a bit rounded
These are a few sutle hints but are in most cases easy tools to sex them
Oh and if they have eggs/fry in there mouth they are female lol
Hope this helps a bit if u look u can see these differences easerly