Just because I'm curious.

[TianTian]

So I know y'all are familiar with Tian-Tian, my male veil-tail (that's a tongue-twister!).
Read: I'm NOT planning on breeding him (frankly I don't need his offspring inheriting his bad immune system, lol).

I've just been thinking about getting another Betta this summer... and I'd like to get a female. Just to be different.

My questions:

1. What are the general rules of thumb for selecting a healthy female?
2. Is there a specific ratio for tank size vs. number of females in the same tank?
3. (and the reason why I'm posting this thread here)What is the breeding age for females (or how can you tell when they're mature)

I don't have the means or time to raise fry, so I can assure you I'm not gonna be breeding anytime soon. I just was curious.

I'll probably have more questions later, but I need to scoot off to class. See y'all!

[Nataku]

Selecting a healthy female is similar to a healthy male when you are looking at a store. You should look for good color that isn't faded and pale, inspect the scales to make sure they are even and tight fitting (aka not doing the pre-dropsy puff). Bring a flash light and shine it on the fish to make sure you see no velvet, ich or finrot which can sometimes be difficult to spot otherwise. Make sure there's no parasites hanging off the fish. Watch for gill movement, the gills should rise and fall evenly on both sides of the fish, they should be able to fully close against the side of the fish. Observe the fecal matter for color and consistency. You want a fish with dark brown poo, not white stringy gunk.
It is more difficult to detect bloat in a female, as most of them will have protruding, round bellies anyhow because of eggs, but any female that tilts to her side when she stops moving should be considered to have bloat/SBD.
In general, the smaller the female, the younger she is. And some of those females are tiiiiinyyyy.

If you are planning on keeping females together, then I would go no smaller than a 10 gallon. Females should be kept in groups, so at least four. If you go by the ratio of 2.5 gallons per betta, the minimum tank size to have the appropriate minimum of four females together is a 10 gallon. 4 - 6 is the standard recommended range of females in a 10 gallon, as females can vary in size from being as big as male, to barely half their size. I don't think there's a specific range for females, but I'd go by the same general addage of 2.5 gallons per betta. Maybe slightly less since some females are smaller, but it depends on the individual fish I guess.

Females become able to breed by 4-6 monthes of age. Generally a female over 1-1.5 years of age is too old to breed. You can tell they are mature enough to breed by looking for the clear presence of the white oviposter, and that the female's belly will become noticeably distended with eggs. Older females who are generally too old to be breedable will still have a present oviposter, but will not be as 'bloated' in appreance, as they will have stopped producing eggs, and will have either expelled what they were carrying or reabsorbed them into the body.

[TianTian]

You weren't kidding about those tiny females; I've seen a few where I tend to shop now for Tian-Tian's needs... and WOW those little ladies really are tiny!

Also, would you happen to know a bit about Betta genetics, Nataku (or anyone)? I think if I have another, darker male (read: not Tian-Tian), I'm gonna opt for a lighter female for an interesting color combination. How would that be figured, genetically-speaking?

[Nataku]

I've read a fair bit up on betta genetics, but me trying to write up a post on them here would be ridiculously long and drawn out.
....besides, there's other pages that have already explained it nicely with pictures and everything else that I probably couldn't fit in a post, and I'm lazy this morning xD
Betta Genetics
Start out with that one, it's a nice, simple easy introduction to genetics for those who have maybe been out of their bio-classes for a few years and need a refresher course on punnett's squares.
And from there go on to a myriad of other sites on the topic.
BETTAS by Jim Sonnier/genetics
^There's several pages on it there, remember to click through 'em.
http://vanriel.myadsl.nl/BT-AABcolorgenetics.htm
^Probably one of the more detailed betta genetics pages out there.
Betta Splendens - Half Moon, Double Tail, Crown Tail Bettas - Genetics Study
If you've got a lot of time on your hands, you're bored, or you're deathly curious like I am, this is a fun site. There are literally hundreds of articles here on bettas, on pretty much every thing and anything relating to bettas. Hopefully the category section I linked up is the one that brings up genetic related articles.

[TianTian]

"O' Punnett Square, you are so fair..."

I'll be checking those links out. Thanks!