water temps change sexes?

[freshfishies]

Will changing the water temperature (gradually obviously) really help determine what sex my live bearer fry will be?
If so...what produces what???

Thanks!
Jazz

[Fishnut]

I think that's a myth...at least with commonly available live bearers

[freshfishies]

That's what I've been thinking, because really all it comes down to is genetics.
Thanks!

[Blackstitch]

I remember having pineapple swords a few years ago, and most of the females eventually turned male. Not sure exactly why that happened.

[dan2x38]

Not sure about live bearers but apistos will produce large amounts of males if the temp. isn't right. If set at 79* you get a better ratio of m/f. Some fish morph in a harem from male - female and vice/verse - mostly in saltwater but some freshwater I've heard do as well. So anything is possible. I'd post on http://livebearers.org/ for the real answer.

[Montrealguy]

Research actually shows that it isn't always down to genetics. It's environmentally determined in the first few weeks after hatching. Since livebearers hatch internally, I'm not sure how that works with them. The only study I've found (on guppies) was inconclusive, because while it found differences with ratios and temperatures the mother was exposed to, it wasn't clear if other factors were at work. The jury's still out.

Cichlids and killies can be determined by temperature, water hardness, hormones in the water and other factors. It's a species by species thing, so there's no magic bullet to help you control ratios.

Swordtails develop sexually in two waves - there are early males (shorter lived) and late ones (tougher, heavier bodied and inclined to take double the time or more to get gonopodiums, let alone swords). Plus, dominated males will have the appearance of sexual characteristics delayed by their status. A lot of the time when we buy what we think are females, we're actually getting 'second wave' males. They aren't changing sex, but suppressing their sexual maturity so the alpha won't kill them. With my montezumae swords, I had one alpha male in a 50 gallon. He keeled over and within days, I had seven 'females" in a race to grow giant swords. Now that I have multiple sworded males in there, the young males seem to be able to pop swords pretty easily.
I breed wild-type swords, and I can't sex them with 100% accuracy until the females are gravid.

There is species by species research on temperature and sex ratio available on the web, just as there are technical articles on the whole sworded/unsworded male thing with swordtails. It's not the easiest reading, but it's out there.

[Fishnut]

I got some wild swords a couple of weeks ago from an OVASer and there were quite a few "second wave" males in the tank I guess.  There was a couple smaller mountain swords with the male fins and gonopodium but quite a few that were the size of the females but they had developed a tiny sword and just developed the gonopodium.  I got one of these larger males with the other species of wild sword, so I'll see how he develops!