How to define the gender of my Pleco?

Question

I dunno whats its exact name but all i know is that its a yellowish pleco. This is how my pleco look like, i found it in google but this is not my pleco.

http://farm1.static.flickr.com/22/28509531_31084b8089.jpg?v=0

Answer 1

The fin on top is how you can tell. If it is curvy then it is a male and if it is straight then it is a female

Answer 2

I've asked a petstore employee, they said that it is impossible to tell the s*x of your PL3C0 unless you have 2 in your tank and one of your pleco is pregnant.

Answer 3

You wont be able to s*x juvenile common plecs, there is no external differences.

As adults it's possible, but not easy to tell them apart.

Ian