Maybe for some kinds of fish. Most stories are hearsay, and I'm not aware of
any confirmed studies in rainbows, but maybe the experts can correct me.
> If so, what pH
> ranges will produce more males? Also, if it is more acidic that produces
> more males, what are some good (easy, inexpensive) ways to get acidic water.
That depends on the original alkalinity of your water (KH). If high (>5), it
may need to be diluted with RO or distilled water to get it down. Then,
boiled peat does a great job of gently acidifying the water in a fairly safe
way. It can be used as a substrate (too messy for some), or in a fine mesh
bag in a filter. [Just hanging the bag in a tank is pretty worthless, IME.
Not enough circulation.]
> For instance, can I just add vinegar to lower pH (I'm assuming not, but
> why?)? My local water is about 7.4 and I get about 60-65% females
> (estimate).
Once the acid consumes all the alkalinity (usually bicarbonates) the pH can
crash with such strong acids and give the fish severe acidosis problems.
Until the crash, the pH will strongly resist lowering (a phenomenon known as
buffering). The more gentle humins in peat seem less disposed to cause a
catastrophe.
>
> Any other controllable factors affect gender?
In some killies, the males just get bigger, first, and eat all the females.
Some folks swear water hardness is a factor. Temperature is certainly a
factor in some Rivulus species, AFAIK.
There is also the propinquity factor. I once knew a Rivulus breeder who got
50:50 ratios all the time. He put two baby fish in each plastic shoebox, and
they invariable became a pair.
For most fish, gender isn't as certain as our having X-Y chromosomes.
Conditions during the first weeks after hatch often have more effect on sex
ratio than at any other time. In addition, many "males" are dominated by an
alpha male, and may continue to look just like females (protective
coloration) until they are separated and raised by themselves. I just
encountered that in a "pair" of Aphyos that I recently separated for
breeding conditioning. I now need a pair of girls.
Wright
-- Wright Huntley, Fremont CA, USA, 510 494-8679 huntleyone at home dot com"When you come to a fork in the road, take it." --Yogi Berra
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