Kribensis

[neon]

Well, I still don't think I have a female Krib.  I was sold a pair at LFS, the male harrassed the other one (not sure if it was a male or female), and it ended up dying.  Purchased another, was told it was a female, and whenever the big male sees it, he attacks it.  I'm sure this isn't mating behavior.  The male has a diamond shaped tail, and is large, with violet coloured bottom fins.  The other one is smaller, with a more rounded tail, but also has lower violet fins.  Neither is displaying a red abdomen.

[beowulf]

Spade vs Rounded tails are a good indicator of make and female.  I noticed my male has a more red belly and the female is the violet one.

[neon]

Guy at LFS told me last night that males can have rounded tail fins.  He said the indicator he uses is the anal fin in males is long and pointed, in females, its rounded.  Both of mine definately have long and pointed anal fins.

[Brine]

I had a similar problem. I went to Big Al's Innes and Jody was able to sell me a "definitely male" Kribensis. I think they are spawning now. At least the new male and one of the females have taken possession of the rock pile and the male is more aggressive now than at first. He will chase anyone away from the pile. In fact he has this funny behaviour of coming out of the pile at the most incredible rate of speed only to find no on to chase. He looks around amazed that there is no one to dominate and turns dejectedly to return to the female in the rocks. Hilarious!

[beowulf]

I think it depends on the age of the fish but once they reach a decent age, the tale fin has never failed me.