General Sexing of Plecs

[KnaveTO]

I remember reading somewhere that a simple way to sex plecos was to watch who starts taking up residence in a cave all the time. The cave dwellers are typically male. Is this true or can it actually be that simple?

[Zebrapl3co]

Mostly true from what I can tell. But some agressive females do take up caves too. So it's not a %100 way to sex a pleco.
A better way is to flip them upside down and look at their anals. If it's round, it's most likely female, and if it's pointy, it's most likely male. Err... note I said most likely. You can't bee %100 until you've seen the spawn.

[windy1958]

the way i sex my plecs is males have a wider pectoral bone than the female.
males also get more hairy pectoral fins and also longer odontodes on the side of there heads.