Hi Matt
The following link is a good start.
http://www.zebrapleco.com/core/hypancis ... s_info.php
As a general rule it is usually quite difficult to sex the fish until they are at least 2.5 - 3 years old. Hence the difficulty in buying captive bred fish. In most cases people tend to sell the young before they reach this age, so gettign hold of a mature group is very difficult unless they are already established.
In general however I look at the following:
Mature fish:
1. Males have more pronounced odontodes (hairs) on the front gill plates.
2. Males have more hairs on the ends of the pectorial fins.
3. Males have a more triangular shaped body i.e. if you were to draw a line fron the gill plates along the side of the body the would intersect at the tail, it would form a triangle. However if you were to do this for the female the lines would not meet at the tail as the body is more rounded.
4. The Gill plates tend to protrude making the shape of the males head more spade like.
In Younger fish, the odontodes and gill plates have not matured, hence it is difficult to use these to differentiate between the sexes, so I look for the following.
1. Body shape as above, this works only with well fed fish. i.e. the female is often more rounded.
2. The females heads can look almost pinched at the tip.
3. the Pectorial fins can be slightly finer and tend to me more rounded. i.e. in an arc. (although to be honest I have never been able to verify this one).
From a behaviour point of view, the most obvious sign is that the males take up a cave. However this can be misleading if the tank does not have enough furniture for the fish.
The easiest form of sexing is however the following:
The one that lays the eggs is the lady!
If I get a chane over the next week or so I will make up a little sticky with some illustrations and photos that I will put onto the forum.
If anyone wants to contribute with pictures etc they are most welcome.
Rob