The twins

Nephthys and Osiris are my twin halfmoons.  They live together in a 10 gallon divided tank, where they've lived ever since I bought them as babies about a year ago.

Their colors are blue and red/orange, so I designed their tank to sort of complement that.

They enjoy their home, but there was something that bothered me.

Some way, some how, Neph was sneaking into Osiris' side.  Regularly.

As in, at least once or twice a week.

And I had no idea how she was doing it.

Of course, as soon as I saw it, I would have a mini heart attack, immediately scoop her up, and put her back on her side.  And that would work for a couple days.  Until she'd go back over again.

I mean, I guess it wasn't a huge deal.  Osiris will flare and charge whenever he sees another male, but he was always gentle with her.  Of course there was the occasional nip or chase, that's to be expected.  It was his territory, not hers, and bettas are just a smidge territorial.

I had a sorority, once upon a time, and the occasional nip or chase was inevitable.  You had to really learn how to judge the fish's character and personality to minimize harm, as well as knowing a lot about their psychology and habits in order to keep them feeling safe, secure, and content.

Because happy fish are generally less aggressive than stressed or scared fish.

It's still not something I would recommend for a single male and female in a 10 gallon tank.

But I've never seen her injured or noticeably stressed from her visits.

Still, they're adults now, and I decided I needed to put a stop to this happening.  They were almost the same size when I got them, but now the size difference is significant.  As he matures into adulthood, he's only going to get more territorial.

His familiarity with her has made him more tolerant of her in his territory, but chances are he wasn't going to allow it for long.  Especially in a 10 gallon tank.  It's just too small.

So I sat down in front of the tank with a margarita and a book, and watched.  For almost two full days.

And finally, I saw how she was doing it.  She was slipping through a tiny gap between the divider and the glass.

Awesome, cool.  So I fixed it.  Problem solved.

Except it's not.

Nephthys is pissed.  For the first few days afterward, she spent most of her time swimming up and down along the divider, trying to wedge herself between it and the glass.  Seriously, she was obsessive about it.

And when she wasn't nosing the gap, she was nosing around the gravel, like she was trying to dig underneath it.

She's normally so mellow and laid back.  It wasn't like her to be this neurotic.

And even Osiris was spending more time along the divider, as well.

It's obvious they miss each other.

But they're going to just have to get over it.  They're adults now, so not only is aggression an issue, but so is the possibility of breeding.

Neph is a growing girl.  She's horny.  And females are every bit as aggressive as males.  The fact that she could fit through the gap, while he couldn't, meant that she very well might eventually decide she wanted his side as her territory, as well as hers.

Because she had a hiding spot if she needed it.  If he ever got too aggressive, she could slip back to her side.

But Osiris doesn't have that luxury.  He was too big to get through the gap, so he couldn't get away from her if he needed to.

And make no mistake: the males are bigger and stronger, but those fins are heavy.  They slow the males down, make them less aerodynamic, and wear them out.  The females don't have that problem.  They're quicker, more agile, they can dart in and out, and those big fins make big targets on a male's back that a female can take advantage of.

So Neph's safety wasn't the only concern.  She could do some damage to Osiris too, if she wanted.  And while she's very mellow and doesn't seem to have an aggressive bone in her body, the fact that she could come and go as she pleased, while he couldn't, would absolutely encourage a sense of ownership and entitlement of his territory as well as hers.

And that's not even touching the breeding problem.  They don't care that they're related.  And in a space that small, it's almost guaranteed that they would breed.

Domesticated bettas are already pretty inbred as it is, so while inbreeding isn't attractive, chances are the fry won't suffer from it.

But there are a lot of them.  And I don't have any kind of equipment to handle betta fry.  Or anywhere to put them.

Because if I were to sell them, I would obviously tell buyers who the parents are, and that they're siblings.

Do you want to pay $10 for a fish whose parents are brother and sister?  Because I don't.

So they've slowly been adjusting to their new solitary lives.  I'd love to have another sorority, so down the line it might be a good idea to get a 50 gallon tank, and let Osiris in with Neph and the sorority.  I've read about people having success with a male in with a sorority, as long as the tank is big enough, but as I've never personally tried that.  I would have to research the hell out of it first.  And they'd definitely need more space than the average sorority.

I had my sorority in a 20 gallon, and I had to juggle females around to make it work, because that's a lot of big personalities in a not-huge area.  I wanted 6 females in the sorority, and I ended up buying 9 total, because I had to mix and match personalities until I got a harmonious combination.  So obviously I needed spare tanks for the other three.

There's no way I could do a sorority with a male in a 20 gallon.  I've never had Osiris with other females, but whenever he's seen another male, he's flared and charged.  Is he only gentler with Neph because he's so familiar with her?  How would he be with other females?  How would other females be with him?

Nope, I'd need at least a 50 gallon for that.

So as the days have gone on, they've gotten less obsessive, and they've realized they can still see each other trough the divider.  

Once they adjust, they'll be fine.  But I'm not having any babies and I'm not having one of them die because Neph is stubborn.