when can you accurately sex GBRs? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 9 Old 05-23-2012, 02:44 AM Thread Starter
when can you accurately sex GBRs?

hi everyone,

i got a group of GBRs from a local breeder a while ago, 6 of them. they were born march 8th so that would make them a bit over 2 months old. i have them chilling in a breeder box for now til i get my 40 gallon aquarium set up.
my question is when can i accurately sex them? as of now, it looks like i have all females. they all have black on their pelvic fin which is indicative of females? so far the blue spot hasnt shown up yet and the pink bellies either. none of the fish have a elongated 2nd dorsal ray either.
ill attach a picture to show 2 of 3 of them. but am i trying to sex them too early? should i wait a while?
thanks :)
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post #2 of 9 Old 05-23-2012, 04:47 PM
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I don't know where you heard that only females have black pectoral fins but that is not true. It may be true in wild type rams, but GBRs have pretty diluted genetics and often color based sex characteristics can not be trusted. If it were me and I was trying to sex them I would take them out of the breeder box and let them settle in. The easiest way to sex rams is to observe there interactions with one another. Once they start pairing it is pretty easy to tell the males and the females.
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post #3 of 9 Old 05-23-2012, 06:00 PM Thread Starter
i read it in a lot of forum posts about the main characteristics to sex GBRs. here on this site as well as on other ones (plantedtank, aquatic community) the most common ones through all those forums or articles were the black stripe on the pectoral fin, the sheen on the blue spot, and pink belly (with pink belly being 99% accurate as a gender determinant). some had a thing about a pointed ray on the dorsal fin but that was not common throughout all the threads i looked at.
im just looking for a time period when i can sex them. apparently GBRs mature at 4 to 6 months so hopefully by that time i can accurately see the features. in about a week or so they will be happy in their new tank. for now its in a shared quarantien tank so i'd understand if they arent showing colors now.
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post #4 of 9 Old 05-23-2012, 06:11 PM
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Most GBR lines have been so inbred and overbred that males often display female characteristics and vice versa. I have heard of all the physical sex characteristics, elongate ray on the dorsal fin, rounded caudal fin, blue showing through on the black spots, etc. The only one I trust is the pink belly, everything else has been proven in my experience not to be reliable.

Just as an example here are my male and female Rams (proven), as you can see both have blue showing through on the spots.

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post #5 of 9 Old 05-23-2012, 07:23 PM Thread Starter
oh ok i see. i did not know that about GBRs. i see the pink belly very clearly on your picture. this gives me much more hope that the ones i have will have some males scattered in there. im going to be moving them soon. hopefully by then the colors will begin to show more.
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post #6 of 9 Old 05-23-2012, 09:17 PM
Thanks, Pandemonium and Lorax. Going by pelvic fins and blue on black spots, I bought four females and three of them beat the snot out of the other. :)
S/He is in a tank by himself, recovering and doing well.
The pink belly is the only certainty?
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post #7 of 9 Old 05-24-2012, 12:01 AM Thread Starter
the pink belly i think is the most certain. i have read of one other GBR owner out of all the forums i browsed who had a male with a pink belly but that as you can see, its extremely rare if not impossible. as far as i know, pink belly is a good indicator of a female GBR.
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post #8 of 9 Old 05-24-2012, 02:24 PM
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Honestly the best way to tell sex is through observation. In the picture I posted above you can see how close together the two fish are, they are like that 75% of the time when they are bonded. They will move around the tank as a pair. Additionally males will chase away females and other males, I have only ever seen my female chase other fish when she is sitting on eggs. I happen to have a great LFS, so they were able to pick me out a bonded pair from a tank that had about 15 fish in it. I know most are not that lucky. The distinct sex markings like the pink belly did not appear until the fish had settled into their tank.
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post #9 of 9 Old 05-26-2012, 10:38 AM
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I agree, the only certain method with young fish is observation. Males will select their own female and the two will usually form a bonded pair for life. This is without question the best method if you want a pair(s) to spawn successfully and live normal lives. You cannot put any female with a male, he may or (more often) may not accept her. As you have a group, let them make their choices; it will be obvious by behaviour.

In mature fish, the diameter of the ovipositor (breeding tube) is perhaps the best method; the female's is thicker than the male's. But this is difficult to determine in immature fish.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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