Tropical Fish Keeping - Aquarium fish care and resources

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Falina 12-08-2007 10:52 PM

Sexing young guppies.
Not really a question, more an observation, but if anyone has comments they would be appreciated.

I've got quite a lot of guppy fry at the moment. 4 are from an older batch and about 30 from a more recent batch.

The first 4 are approx. 4 months old, I haven't really been keeping track of their age, though I wish I had now.

At about 5 or 6 weeks old I had, or at least I thoguht I had one male and 3 females. The one male was developing bright colours and had a definite male anal fin. I left the male in my community tank and put the females into a 15g grow out tank to prevent inter-breeding. All was well. One of the females has developed slight colour and snakeskin pattern on the tail over the last week or so but it was very faint. Tonight I noticed he said female chasing anoher female around the tank a lot so I took a closer look - the female is definitely a male! When I started noticing the tail pattern I checked again for the male anal fin but it wasn't there so I thoguht nothing of it as many females do have coloured tails anyway. Only tonight has it been evident that the anal fin is male.

I was just wondering what you guys thoguht about this. Maybe it's nothing unusual, I don't know - this is my first batch of guppy fry. I just found it quite odd that there was such a space between the 2 males developing their male attributes. There is at least 3 months between one being apparently male and the other, though it might be more than 3 months, 3 months is just a very conservative approximation.

tangy 12-09-2007 01:34 AM

I have gone thru this once with gray feeder guppies(I think they are also called mosquito fish-not shure tho). Two females were bought to feed to Steve but he never really went for them. One dissapeared for about a week. I thought Steve eaten her but when it popped up later it had an pointed anal fin. In a few days he vanished completely when I mixed in a bichir, as well as the female's eye. Thats right, my current feeder guppy has no left eye :? She still rocks. :D

bettababy 12-18-2007 01:33 PM

One thing to keep in mind is that fish mature much like people... everyone at their own pace. My sister and I went through our physical developments at different ages as babies and teenagers... fish are not any different there. This is why those of us who breed livebearers keep a close watch on them for a long time to keep them sorted.

fish_4_all 12-18-2007 01:58 PM

So true. I have had guppies, swords and platties play the waiting game and mature so much later than others in the tank. So many times I thought I had females and then 2 weeks later they turn out to be males.

Must be the fish making sure they are in control while giving us the false impression we actually know what we are doing, lol.

bettababy 12-18-2007 02:26 PM

Also, I'm not sure about guppys, will have to check, but I know with mollies they are dimorphic... they have the ability to change sex to ensure survival. My gold dust molly did this to me recently, much to my dismay. I had 6 chosen specific females in the tank and added 1 male gold dust to the group. These are/were adult fish, and it even appeared gravid when one day I noticed it chasing down a black female... I was curious, as they'd never bothered each other before... and sure enough, it was now male. This fish has now father'd multiple spawns with the females. I have to assume the other male fish is sterile, as before this happened none of my females were getting pregnant and now I have fry coming out of my ears, every 30 days another spawn.
Mother nature is capable of some amazing things!!!

Falina 12-18-2007 05:33 PM

That's interesting. I guessed that they would mature at different rates, I just didn't expect such a large difference to be normal.

I'll just need to keep a closer eye on them than I first anticpated. Not a problem.

Thanks. :)

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