Goodness, MrV - since I just recently started my sorority - reading this from you (who has lots of betta experience) is rather daunting - PLEASE dont tell me that I'll eventually have to break up my big tank ...
So can you tell us what the details were on this tank? dimensions? how many girls? well planted? lighted or dark? ...
And how long does it take for a betta to reach maturity?
It was totally unexpected.
Tank size: 10 gallons
Female count: 3, 4 a few weeks ago but one died.
One live plant and several plastic ones.
These females are old so that dosen't help the situation much. I'm not sure what ahppened. The history of this tank has not been so great:
Females introduced in December 2008.
First female dies in February 2009 (symptoms: Laying on bottom, not eating, breathing heavily). New female purchased.
Second female dies in March (same symptoms as above). New female bought.
Third female dies in June 2009 (dropsy, luckily she had been removed from the tank before it happened).
New female bought July 2009. (count up to four). Female dies.
August 2009. Fight breaks out.
So total: I lost four from this tank. Two of the original four females are still alive.
First, I don't think you'll have a problem as long as the alpha female is in the tank. I'm not sure what happened. Hopefully it dosen't happen to you.
The reason I tore it down was because: it needed a good cleaning and two because I figured an extra spawning tank would be useful.