Ideal temperature for ideal sex ratio

[Happyfins]

Hi guys,
I'm after a quick guide for my species to get closer to 50:50 sex ratio.
After breeding almost exclusively female cacatuoides I raised the temp to 26 degrees (celsius) and got more males.
I know other factors influence sex ratio but would like to have your opinion on raising temps for

1. Cacatuoides
2. panduro
3. agasizzi
4. macmasteri.

Much obliged, Chris

 

[Bart Hazes]

Cichlid atlas 1 has a chapter on sex ratio of apistogramma. Some species are more sensitive than others but from memory 25/26C is optimal. If you go higher you get more/most males and productivity goes down. The other factor is pH with more acidic water biasing towards male, but the effect is weaker than for temperature.

 

[Mike Wise]

This is the paper you should read: Römer, U & W. Beisenherz. 1996. Environmental determination of sex in Apistogrammai (Cichlidae) and two other freshwater fishes (Teleostei). J. Fish Biol. v. 48 (4): 714–725.

 

[Happyfins]

Yes, thanks! See, I have the cichlid atlas and to be honest find the chapter difficult to interpret. I wouldn't have a clue where to get the paper from. I was hoping someone would do all the hard work for me and just give me numbers.

 

[Mike Wise]

Use water values in CA1 and 26°C/79°F. Personally, I breed at a slightly lower temperature now. Why? Because I want more females to make trios and female fry tend to be out-competed for food/space in grow-out tanks, so I lose more females.

 

[gerald]

Keep in mind also that the temp effect on sex occurs when the fry are a few weeks to a couple months old, not at the time of egg-laying. So if you find an unexpected new batch of eggs, their sexual fate is not sealed - you can still influence it.

 

[Happyfins]

Thanks for all your answers. I was aiming for 26C, Mike. Definitely need more males. I have 1 male for every 5 females which makes moving them on very difficult.

 

[TCMontium]

Thanks for all your answers. I was aiming for 26C, Mike. Definitely need more males. I have 1 male for every 5 females which makes moving them on very difficult.

With which species at what temperatures did you get 1:5 male-female ratio? Do you know the ph levels they grew in too by any chance?

 

[Mike Wise]

Agree. There are many variables that affect final sex ratios. Temperature is the primary one, but time-at-temperature & pH also have an effect - as does loss of fry of mostly one sex.

 

[Happyfins]

With which species at what temperatures did you get 1:5 male-female ratio? Do you know the ph levels they grew in too by any chance?

Species: cacatuoides, Temp around 21-22c, pH unknown, I don't measure

 

[Happyfins]

Agree. There are many variables that affect final sex ratios. Temperature is the primary one, but time-at-temperature & pH also have an effect - as does loss of fry of mostly one sex.

Also I think I read somewhere (?cichlid atlas) that some domestic strains produce overwhelmingly skewed sex ratios.

 

[TCMontium]

Species: cacatuoides, Temp around 21-22c, pH unknown, I don't measure

That is very cold, as far as I know 25 celcius is approx. the temperature for 1:1 sex ratio without counting the effect of ph. I once had 100% males with 27-28 celcius and 5.0-5.5 pH when I grew 25 A. cf. ortegai "pebas" fry (just 2 deaths from 27 hatchlings).
I assume if your pH is higher than 6.5-7.0 and the temperature is 21-22 celcius, it is very normal to have a 1:5 male-female ratio, if not 100% females. Even with lower pH it probably is expected to have mostly females in the clutch at 21-22 celcius with any Apistogramma species.

 

[Happyfins]

I increased the temp to 24C with the next batch and got about 1: 3 males to females, current batch is 26C so I will see what happens. Problem is I have to breed more males so that I can move my females on. There is a small market for apistogramma here and certainly none for just females although as a single fish they make a nice pet in a community.

 

[TCMontium]

I increased the temp to 24C with the next batch and got about 1: 3 males to females, current batch is 26C so I will see what happens. Problem is I have to breed more males so that I can move my females on. There is a small market for apistogramma here and certainly none for just females although as a single fish they make a nice pet in a community.

If you have many females already waiting for males, then you might want to increase the temperature not just to 26, but to 28-29. This will make sure that most of the fry are going to be males, if not all. And they will grow fast! But there is also the idea that if you keep the temperatures too high, then the overall lifespan of the fish will be very short. So, you might not want to exceed 28C, if you think it is too risky. (I do not know any actual experiment and data about the "hot and fast youth = short life" idea, I just read about it on a thread, it may not be true)

 

[Happyfins]

Followup: My batch raised at 26C produced exactly one male. And now it seems my Aphyosemion striatum fry are also 100% female. I know it's not apisto but does anyone know the ins and outs of sex and temps with these?
When I was after girls I didn't get them and now I'm drowning in them.

 

[Bart Hazes]

If you were at 24C I'd say boost it to 26C but you are already there. You can increase the temp more but egg/fry viability starts to go down as you go warmer than 26/27C. The temperature and pH effect on sex ratio is somewhat variable between apisto species so I don't think there is a fixed 'ideal temperature'. But I would say 26C should be high enough.
Are you sure you have all females because all fry start out looking like females. In other words, are they old enough to be sure that males should have shown their maleness by now?

 

[gerald]

I wonder if the various plastic and rubber items we use in our tanks, and/or household products and skin-care products, may have chemicals that disrupt endocrine hormones and affect sexual development in fish, in addition to temperature and pH effects?

 

[Happyfins]

If you were at 24C I'd say boost it to 26C but you are already there. You can increase the temp more but egg/fry viability starts to go down as you go warmer than 26/27C. The temperature and pH effect on sex ratio is somewhat variable between apisto species so I don't think there is a fixed 'ideal temperature'. But I would say 26C should be high enough.
Are you sure you have all females because all fry start out looking like females. In other words, are they old enough to be sure that males should have shown their maleness by now?

Having had several spawns of cacs now and having raised them to adolescence I am pretty confident I am getting the sexing right. Most importantly, when I remove the obvious males no sneakers declare themselves which I assume they would. Not so sure with the striatum, I remain hopeful and probably am just impatient, I guess they are about 3 months old. Had a look at them the other day and there are fat and more athletic looking ones, the latter I'm hoping might be males.

 

[Happyfins]

I wonder if the various plastic and rubber items we use in our tanks, and/or household products and skin-care products, may have chemicals that disrupt endocrine hormones and affect sexual development in fish, in addition to temperature and pH effects?

Good thought! Though I would assume it would affect my agasizzi and panduro in the same way but not the case. I cannot get something out of my head that I read in Römer's cichlid atlas in regards to cacs and that was that some inbred strains produce extremely skewed sex ratios.

 

[Happyfins]

Do temps and pH affect different species in different ways? My panduro produced overwhelmingly male offspring. My cacs a s mentioned above overwhelmingly female. My agasizzi pretty equal amounts of male and female.