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What age before you can tell a Platy is male or female?


NoFishing

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Hi Guys

A couple of months ago I bought 4 Platys as they were a nice red and thought they would add a bit of colour to my community tank of Neon Tetras, Harlequins and Dwarf Gouramis. Little did I know however that of the 3 of the 4 were females. Needless to say I soon had little platys swimming merrily around.

I have another smaller tank (AR380) that is the home of a male Beta. I decided to put the fry in with him and let nature take it's course. The first batch of about 4 disappeared quite fast. The second batch however had much higher numbers and they were harder to catch in my planted Vision 260 so I left them to grow out a bit before moving them to the smaller tank.

I probably left them a bit long as of the 15 I put in with my Betta, 9 still remain and are big enough now to steal the food at the top off my Betta. (I feed the little guys with NLS small fish size pellets on the bottom and the Betta gets the Betta version at the top) The two tanks are right next to each and it's interesting to watch the Betta flare up every time the adult Platys swim past, and yet he pays very little attention to the teenagers in his own tank. He did chase them very enthusiastically at first but soon tired of it when he couldn't catch them. LOL

I don't really have the heart to cull these guys myself as I find them still cute and very entertaining to watch. So I had thought I would just keep the females only and put them back into the big tank once they are big enough to be able to tell who's male and who's female.

Currently they are about 1.5 - 2cm long and they all look like females. (going off the lower fin) Is that because they are still too young, or is there a good chance they are in fact all females?

I will also find a new home for the adult Male so no chance of the cycle continuing.

Any advise would be appreciated.

Cheers

Leon

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I would have thought that the gonapodium would be showing on males at that size.

Cool thanks. So they are born with the gonapodium already developed? I was under the impression that as they matured their lower fin would turn into one, or at least the appendage would become more evident.

Cheers

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Sexual development has HEAPS to do with the line the fish has come from. Have had platys and swords that have been one gender their entire lives, grown huge, never produced fry then suddenly turn male. but at 2 months old generally (especially if in large numbers) the gender should fix and be obvious. Livebearers have the ability to be very diverse fish!

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You may find that if you do keep only females one will change sex.

from the net (this is bound to cause discussion :lol: )

Platys don't change sex, but there are two times in their lives when they can confuse their owners in this regard. All platys are born looking female - if you have a look at some newly born fry, all of them will have the triangular anal fin of the female. As they get to about 1/3 adult size, some of them will start to show that they are males by developing the gonopodium (male-shaped anal fin.) If the tank is overcrowded or they are underfed, this might be delayed until they are almost full-sized. This is more noticeable with mollies and swordtails than with platys; sometimes these fish can appear female until they are over a year old, if they are in the same tank as a dominant male. When separated from the dominant male, they suddenly develop male characteristics.

The other time when they can get confusing is very old females. Sometimes an old female will stop producing fry and may even develop a gonopodium. She has not actually changed sex; she is now sterile and will not show male sexual behavior or father fry. This happens to some females but not others, and again is more common in swordtails.

(The last paragraph is what happened with one of my gold lyretail mollie breeders)

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