sexing a bristlenose

[Analog Saint]

I have 2 x 2" bristlenose plecos, and I was wondering how to sex them... More for compatibility purposes than actual breeding purposes. Thanks.

[Lucretia]

once they get a little bigger around 3inches or so they will form bristles on there face hence the name the male will have quite a few bristles whereas the female wil have only 2 i believe

[racingjason]

It depends on the type of bristlenose it is. In some the males have a "beard", in others they get a whole head of bristles. Wait until they are a little older and you will be able to tell for sure.
The male I have in my large tank should be wearing a wife beater t-shirt, he is the laziest fish I have ever seen! Just peeks out of the cave to grab some food and then right back in! :p

[Blinky]

They should be fairly easy to sex by ~1.5", based on some of the reading I just did (Googled 'bristlenose catfish male female'). Males develop a head full of bristles, females have just a few along the lip or sometimes none at all.
I adore my bristlenose (Ancistrus claro). Looks like mine's a male - he's very bristley ;)