female bettas keep dying?

[trojannemo]

hey guys and girls.
i've got a 38G tank with admittedly a lot of fish, though water parameters are always great.
now, i had a male betta for the last 4 months or so, and though his tail kept getting bitten, he was doing great.
then we stumbled onto a fish show and exhibition and bought what they called a "Rosetail betta" female. very beautiful. she was doing ok for about a week. i noticed that my male kribensis, who has never been the one to attack his tank mates, began following her and nipping at her. she died, less than 2 weeks after introducing her.
i didnt know if i should blame the male betta or the kribensis.
my fiancee had fallen in love with female bettas at this point, so we got and get a red/white regular female. she's always hiding until the male betta dies (don't know cause of death).
now she's out and about, and i notice the kribensis following her too. so he seems to have something against female bettas (mind you he never bothered the male).
then to replace the male betta, i got another female who was his same strong blue color, hoping to reduce the tension in the tank.
day later, the white/red female is dead....

i keep checking my water and parameters are fine, so it's got to be a fish compatibility issue no?
is it normal for kribensis to not get along with female bettas? more to the point, was that rosetail "female" really a plakat male? (didnt know they existed at the point)
any help would be greatly appreciated.

now i've got two dead females and a dead male. only one female (the last one, blue) remains. i really enjoy bettas, and would like to keep 2-3 females and a male, but i dont want to keep adding fish knowing they will die!

 

[skratikans]

From this post, I would get rid of the male krib. He is most likely the cause of the female betta's demise. Male bettas are known to harass females as well that can also lead to death...however with the male krib chasing the female I would remove him for sure..
I also see the krib isnt playing nice to the male betta either. Generally, this trio combo is not a good idea to have. I would get rid of both the krib and male betta if you have your heart set on female bettas...you can keep a group of them in your tank

 

[TabMorte]

Krib + Betta = Bad combo

Bettas are territorial but Kribs are Cichlids and territorial in a whole differant way. Cichlids communicate a lot through the colors of their bodies and it's very likely that he's reading things in the colors of your bettas (particularly if they're red, this is the color female Krib's bellies turn when they're wanting to breed).

I've kept male and female bettas together but the trick is getting them very very young, if you get them as adults it's much more diffecult to manage unless you have a very docile male.

If you like the female bettas though I would highly suggest a species tank. A 15 gallon would be suitable for three to four female bettas and you could put some Ottos in (I'd say 4 to 6) to keep the tank algae free. If you planted it it would look lovely and colorful.

 

[sheamurai]

so what did you settle with?