Cockatoos fry (Cacatuoides) 100% females !!

[MrsShytwn]

I've hatched 2 batches of cacatuoides eggs (67 live fry from each batch).

The first batch is now 1/2" to 1" @ 13 weeks old
The second batch is upto 1/2" @ 8-1/2 weeks old
I have 130 fish in a 29gal tank, and I have 130 clear tails.
No males, 100% females. I know you're thinking "No Way", that's impossible, you have to get at least one male out of 134 fish/ from 2 batches. Well it is possible... because I've managed to do it with my first 2 batches of apistogramma cacatuoides.

Water parameters:
pH=7.8
hardness=120
ave temp=84+ (summer spawn in Chicago & I refused to turn on the A/C to keep the tanks at optimal temps).

The water seems to be okay because for several months the female was spawning every 2 weeks. And I thought that high pH and high temps were supposed to produce a higher ratio of males. Well I've managed to produce the exact opposite.

I grabbed the largest new female in the growout tank and relocated her to the 75gal community tank (where my pair of cockatoos live), just to see how the male would react. Well he sniffer her out immediately, and 5 days later she's laid a batch of eggs (@ only 13wks old). So my fry are healthy and obviously thriving, but how did I end up with ALL females??

I've invited a couple WI cocktoos fellas to come and join my family.
I expect them to spawn with my girls almost immediately.
What do I change to ensure that I get at least 1 male in the next batch?
...the obvious difference will be that the tank temps will stay at 78deg.
Will that be change enough?

Sincerely,
Louise

 

[farm41]

I wouldn't judge the sex by the tails, your fish sound kind of young to be determining sex. the ventral fins are better indication, get them in a large growout tank and they may suprise you. Sounds pretty packed to me.

 

[EuJin]

Louise,

I would love to have my nijsseni grow out nice plump and into adults to share with the aquarists in Sydney, can you share how you have brought them up since they were wrigglers? Besides having a good sized grow out tank and good water conditions, what sort of diet and water change regime should I put them on after the wrigglers stage? Will bbs be enough to ensure optimal growth? Thank you.

Yu Jin

 

[fishboy20]

Uwe Romer did study sex ratios in Apistogrammas but found the reverse to be true in temperatures. The higher the temperature the higher amount of males. However pH is also a factor and it would seem that the high temperatures combined with a pH of 7.8 made it so females would be the preferred sex ration in the wild. If I were to offer some advice it would have to be to try raising the fry at a lower temperature and try reducing the pH with driftwood, peat and/or an R/O unit.