Need to influence sex ratio in my breeding

[gwand]

Over the last six months, my golden sailfin Molly pair have produced progeny 3 times. Each time I have raised upward of twenty fry to the juvenile stage before selling them and giving them away. To date every offspring has been a female. I know that water temperature and pH can influence sex ratio. In my livebearer tank the GH is 230 ppm, water temperature 77F and pH 7.3. What parameters can I manipulate to get some males?

 

[fishorama]

I haven't kept mollies, but with kribensis they were temp/sex? dependent. We had batches of almost all males most times but a few mostly females. It may have been something else like seasonal hardness instead of temp., I'm not sure.

Young fish tend to look female for quite a while. Maybe keep the largest juveniles & see what happens?

 

[Back in the fold]

Interesting . My platy’s are overwhelmingly male with females being a very noticeable minority . @GaryE what say you ? I know that serious killie keepers have debated this topic for years .

 

[Colin_T]

Maybe the mollies aren't sexually mature when you get rid of them.
Have you kept any for 6-12 months to see if they turn into males?
How big are they when you sell them?

 

[gwand]

Maybe the mollies aren't sexually mature when you get rid of them.
Have you kept any for 6-12 months to see if they turn into males?
How big are they when you sell them?

Good point. They were 3-4 months old when sold or gifted.

 

[Magnum Man]

my platy's alway sexed out earlier than that but maybe not the molly's?

 

[gwand]

my platy's alway sexed out earlier than that but maybe not the molly's?

So far I’ve raised about 45 juveniles from three Broods and they all appear to be female. Do you think that’s possible? If it is, I wish I knew the variables responsible for this lopsided sex ratio.

 

[emeraldking]

The problem with a serious number of ovoviviparous livebearers is that there are three stages a specimen can sex out. Mollies are one of them. The three stages are:
1: Early males. Such males develop their male traits when they're still small. And they won't become bigger once the male traits are visible.
2: Normal males. These males will develop their male traits as juvenilles and sex out completely at adult size.
3: Late males. These males look female shaped for a long time, even when they hit the adult size. These specimens grow up larger than a normal male and once bigger than a normal male, the male traits will develop.

The influence of temperaure on the sex ratio of the fry will only help if the temperature will be regulated down- or upwards during the whole pregnancy period. So, regulating the temperature later won't help.