Factors affecting sex ratio of Apistogramma fries

[mobile2007]

I noticed that the fries ( caca and trifasciata ) that i raised so far have a high male to female sex ratio. As i have previously mixed in some coral chips into the GEX soil, the pH of the water kept moving over to the alkaine side. I suspected that this is the reason that the sex ratio was skewed that way.

Like to know whether this is true or not? Any other factors affecting the sex ratio? How's your apisto fries sex ratio and water condition ?

Caca and Trifasciata
- ph > 7.6
- temperature 27-29 degC

[exotic_idiot]

My apisto fries like almost even.. Maybe female slightly more than male.. Kept them at a PH level of 6.5-6.8 i guess...

[mobile2007]

ok. thanks, exotic.

[exotic_idiot]

Check out this link...
http://forum.apistogramma.com/archiv...hp?t-2800.html

[Shadow]

Quote from the link:
I've read that section in the Cichlid Atlas, and done my own experiments, which gave the same results as the book.

26C seems to be the "even" point for the sexes.

Higher will give more males.

Lower will give more females.

The more the temperature varies from the 26C point, the more the sexes get more defined, for example, many mores males than females if the temp is at 30C.

That interesting

[exotic_idiot]

Yes, but for singapore temperature higher doesn't mean get more males... Either way have spawn better than no spawn right??? Hahaaa like mine small batch better than nothing..

[mobile2007]

On the web also reported:

1) Lower pH favors more male ratio ( 6.5 to 7 as mid pt )

2) Lower temperature favors more female ratio ( 26 deg C as mid pt)

3) Sex formation in first month of fries development

4) Extreme ( low or high) pH results in heavy ratio of male

Links:

- http://www.thekrib.com/Apisto/ph-temp-sex.html
- http://www.cichlidae.com/talk.php?id=299

[apistomaster]

I have always had reservations about the chemistry and or temperature skewing sex ratios although I do not deny that these things are possible.

I have an alternative hypothesis as to why Apistogramma spp spawns, in general, tend to result in a predominance of males. I think the male fry have an immediate advantage in both growth rate and aggression.
I have tested my hypothesis by covering the bottom of my Apistogramma rearing tanks with hollow ceramic cylinders. This provides far more than one small cave per fry and breaks up line of sight between them. This additional shelter is over a bare glass bottom. The results for me have be far more balanced between the sexes. This early aggression from the males results in fewer females surviving to maturity.
I have been using this technique for 15 years and with many Apistogramma species and the results always seemed to me to be as evenly balanced as one would expect, statistically, based on the assumption one begins with a 50/50 chance for each fry to be male or female.
It definitely helps me grow more Apistogramma fry to a more even size up to the point where they begin to differentiate into their secondary sexual characteristics in a given sized aquarium than I can without that initial sheltering.