The two $20 2.5 gallon tanks I got are from Petco on line. It' on sale for the holidays. (Maybe it was cheaper for me b/c I have a "PALS" card?) but it's the Aqueon Betta Bow 2.5. It comes with a divider, filter and light, $20! (Free shipping!) I added a $15 heater from Walmart. My male is in one w/o the divider. I can insert the divider at any point (I'll have to move the gravel, palnts, etc.). The filter is absolutely SILENT, so it's a super little tank.
You know, I've been hanging around here for three and a half years and I never even bothered taking a look at the eBook.....but if it does say that it definitely should be changed because that is simply not a good idea.
For now, I would suggest constructing a mesh divider, even if you have to do a little 'sewing' and sticking it in the 5 hex. As a temporary solution, this will be just fine until you can pick up a separate tank for whichever girl you decide to move out.
With live plants and filters(and I assume an establishing Nitrogen cycle)going, I don't think your biggest issue here is water quality, more just the risk of waking up to one or two severely injured/dead fish.
I think bettas each have a distinct personality, just like everyone else! I'm sure some females are better at co-habitation that others. I'll bet it has to do with how they were raised- "factory" fish farm vs. home fish breeeder... it would make an interesting study. I guess the takeaway is that you never know until they fight, then it's too late.
My 2 cents: I'm thinking fish-farmed bettas get used to cramped quarters, have a chance to kill the weaker fry, and if they that make it to fish stores alive are pretty adaptable. Home-raised fish are probably a little spoiled and won't like to share!
Just another point - my baby betta from petco had stripes for the first two months I had it. Was well over an inch before its fins grew enough for me to realize it was actually a HIM not a HER. Stripes dont necessarily mean you have a female when they are that small.
That is very true. Bettas certainly do have their own distinct little personalities, every single one is an individual. I've had many bettas since I started keeping a few years ago, and never a single two exactly alike.
And some females do tolerate other females better, and its those traits in a female that would make it good in a Sorority or even alone in a community tank....but while bettas are individuals, while they do have different personalities, they are still an aggressive species of fish. Even if one of your girls is passive, the other will just dominate, harass, and injure/kill her eventually.
Like I said, your girls are still young and they haven't been together very long(correct?), but its not an issue if IF its WHEN.
That is an interesting theory....you know, I really wonder how a fish farm bred and kept their bettas.
However, I've found that females from pet stores are much more aggressive then home-raised breeder females. A Sorority of pet store females is much more likely to not work out then one of breeder sibling females who have all been raised together. I think the fish farms separate out the bettas early on so they can ship them out as quickly as possible, so they don't spend a whole lot of time together.
Since you got your first one as a baby betta, and likely just a few weeks old, it is very likely she could surprise you and turn into a he. Fry are very delicate, and kept in such harsh conditions that some adults can't even handle in the pet stores often results in stunted growth, so they can 'bloom' a little later.