Bas Pels wrote:fully unexperienced in African cichlids, my thoughts go out to Apistogramms, which are known to be pH dependend in sexratio - low pH gives more females
As many of these breed at very low (dangerously low, due to a lack of buffer capacity of the water) most breedser breed them atmax possible pH - thus get many more males than females
perhaps this is also the case for Hemichromis???
It was thought that this was so, but research has shown a much higher correlation with temperature, although pH seemed to influence a little bit in some cases. High temp. yields more males and low more females with a 50/50 ratio about 26 degrees celsius. This is of course an average and will not always work since there are probably also some individual differences (Personally I suspect that the temperature effect could really be an effect of oxygen content, because temp. and oxygen are obviously closely connected. Naturally it is much more feasible for the hobbyist to control temperature, so this has no real practical importance). The experimental work in this area was published as follows: U. Römer and W. Beisenherz, 1996: "Environmental determination of sex in Apistogramma
(Cichlidae) and two other freshwater fishes (Teleostei)". Journal of Fish Biology (1996) 48, 714-725.
I have the paper as PDF, and will gladly mail it to anyone interested.
As for "westies" I think that in many species pH actually does determine sex ratio. At least this is what I read to be true for some Pelvicachromis
spp. I have never heard sex ratio to be a problem for Hemichromis
spp., but then again I don't know a whole lot about West African cichlids.