PlanetCatfish.com

Even fry as small as two centimetres can be sexed accurately if you look very closely.
With L333 catfish and a host of others you will see that the ventral fins are very useful in this.
The L333 catfish tend to be rounded in this area when female while the males tend to have a pronounced ventral ray and be less rounded than the females.
I've found this to be 100% accurate in some species although not all and this does clearly show in truth that they can be sexed even at such a small size if you take a very close look at them please note though that this clearly would be thrown off if there is a deformity in the ventral fin area!
So aquarists take a very close look at you're fish because if you have the eye you might just find that you can sex them easily with a little care and time.
Rohan R

Any chance of a picture to help those of us that find it easier to look at pictures than reading?

When you say !00% successful I expect you mean 100% - how many samples is that on, and how have you verified it afterwards?

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Mats

G'day Mats.P.
I've used this method for years now with only limited species though(certainly not all)!
While i don't have any photo's i dare say that someone will hopefully put up a pic or two or i'm going to have to learn how-lol. Perhaps you might be kind enough to do this as i do care to contribute to the hobby on this and other areas. On the other hand if i'm forced to learn how that certainly won't hurt as that will make this very clear and concise.
Rohan R

Right, "How to add a picture to a post" is not hard. There are two cases:
1. Picture available elsewhere on the internet (e.g. photobucket):
Use image tags with the URL of the photo between tags. shows this:


2. Picture available on your local machine:
Use the upload attachment functionality in the field just below the "Save, Preview, Submit" buttons of the post.
Use the "Browse..." button to locate your file, click "Add the file", and then you usually want to "Place inline" to show the post within the text.

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Mats

In that case i'll have a go at it mate thanks for that appreciated. The nugget there seems to be a girl if you look at the top fin just in front of the tail fin,but don't quote me on that lol as mine(males) tend to be sharp or hooked at the tip of this fin.
Rohan R

The burden of providing evidence supporting your theories falls squarely on your shoulders for the edification of the forum membership.
Please, no teasing.