Guppy fry all females?

[danakin]

I have raised guppies since I started with aquariums when I was 8. Many times I would wake up to find that I had a new batch of babies, and I eventually learned that I could intentionally breed them.

However, my latest guppy fry are a bit odd. There are two batches of them, spaced out about 2 weeks apart, and both were delivered by the same female. The odd thing is that every single one of these lil guys grew up to be female.

I'm wondering if that is just a coincidence, or are there factors that play in to this? My aquarium is in a relatively cold room, but I keep the temperature in low 80s high 70s (I am unable to get the temperature any higher because of the size of the heater and the chilly room). With alligators and the like temperature plays a part in gender determination, but does this hold true with livebearing fish?

Sorry, no water parameters as of yet, been super busy with college finals.

[mistergreen]

it would be a neat science experiment....
In alligators, the sex on the babies are determined by temperature..

Try bumping the temperature down a few degrees and see what happens.

[danakin]

I think I will have to go with a lower temperature for the next month. During Christmas break we turn the heat down low in the house while we all head home, so the ambient air is gonna be much cooler.

Though I predict that if this holds true at all, it would require higher temperatures to yield males.

[spypet]

http://www.plantedtank.net/forums/fi...t-endlers.html

[sandiegoryu]

I know Zebra danios get different for different population differences. If the fish are crowded, the majority become male while if the fish are not very crowded they become female. Or it was the other way around but I think the first way makes more sense.

[susankat]

In endlers, which would be like guppys, the lower the temp the more males. I would get mostly males with temps around 68 - 70. Higher than 74 I would get more females.

[JennysPlanties]

Originally Posted by susankat

In endlers, which would be like guppys, the lower the temp the more males. I would get mostly males with temps around 68 - 70. Higher than 74 I would get more females.

That's weird... my temp in my tanks w/guppies never gets much below 80, yet I consistently have more males than females every time these guys breed. I've got a tank full of guppy males and only 6 or 7 females.

Then again, I never get many fry that survive, even when there were only guppies in the tank. It seemed that 20 or 30 would be born and within a few days only 10 would have made it past being fish food, so maybe males are smarter/faster than the females?

[susankat]

Hmmm, maybe faster, but with the endler and guppy so closely related I would figure it would be the same, but may not be.

[danakin]

Alright, thanks for the ideas. I have set the temperature down to mid to low 70s. Got a batch of babies brewin in the belly of a female as we speak, so we'll see how things progress when I get back from break.

I'll let you know how things turn out. If anyone has any other ideas they would like to test, I am more than happy to try them for you.