With the increasing popularity in those beautifully finned, colorful fish in the store, arguably some of the easiest to obtain and care for, it would be a dream to some to keep a whole rainbow in a single tank. And that is where the sorority comes into play. Recently, I have seen a few questions on sororities in forums and the best methods to have one. I've decided for my first article to be one on keeping a sorority to help clear up any confusion or misconceptions that may exist, as well as highlight the benefits of keeping one. There is so much more than throwing a group of females in a tank and expecting them to get along. It may be a challenge, but a fun experience nonetheless.
So, your first question may be "what is a Betta sorority?" and my answer to that would be "a group of female Bettas that are housed together in the same tank." Yes, the same tank! However sororities can either be a wonderful success or a colossal failure. Depending on what the aquarist does prior to obtaining their girls to selecting the right fish, I have outlined some steps that should help someone set up one of these types of tanks and hopefully tilt the scales toward a successive sorority! Therefore, I do recommend those with intermediate or advanced experience and skills to try this tank out. For the beginners out there, it's probably best to get your feet wet into the hobby using simpler fish to keep. (Please be aware this guide is not for telling someone how to cycle and start a basic tank; this is a guide for everything after that point. So please, if you are unfamiliar with the basics, go read up! There is tons of useful information here on FishLore and the internet Thank you! )
Tank size can be a bare minimum 10g, but any larger size tank is preferred and much easier to maintain. Therefore, it would be better selecting a 15g or 20g as a starter. Additonally, larger tanks allow for the introduction of bottom dwellers that should add interest to the tank, if you so wish. Tanks should also preferably be longer than it it taller; Bettas are natural top swimmers and won't require as much height. However, the key in choosing a longer tank is to allow each female to carve out her own territory. Females can be as aggressive and unpredictable at times, like males, and it is important to provide enough space for the victim to escape the aggressor and reduce territorial tension. Additionally, the more dominant females tends to occupy the surface of the tank and may get aggressive during feedings or when others surface to breathe. The longer size helps in spreading everyone out.
Your tank will need to be on the medium-heavily planted side, along with additional covers for them to utilize; the idea is to block the line of sight. This is also a good opportunity to get your hands wet in planting tanks. Many of the best options for beginners are some of the easiest to grow. Invest in easy plants such as swords, java ferns, anubias, and ancharis; not only will they grow fast and provide cover, they are also wonderful competitors to keep algae at bay.
The number of Betta you can keep is most likely the trickiest part of the whole process. You want to keep a minimum number so a single female is not picked on and bullied, nor do you want to to keep so many that territorial issues arise and they are constantly fighting. Therefore, Bettas should be kept in at least a group of four whereas the maximum number depends on your tank size. Ideally, you'll want to provide 2-3 gallons per Betta. So, a 15g would have 5-7, and a 20g would have 8-11 (the calculations are very rough and flexible. Depending on how well the sorority goes and your aquascaping, you can add an additional 1-3. The flexibility also accounts for adding the additional Betta, but more on that later). Furthermore, keeping numbers odd will additionally help the hierarchy (thank you @FlutterFish).
*Edit: In an earlier version of this post, I had mentioned that a 10g stocking should house 4-6 females. However, I have realized that some consider this an unfavorable idea. My personal take on this is that in a 10g, there is always an increased chance for aggression, but depending on your stock, it may produce a peaceful society. Therefore, depending on your own experiences or beliefs, it may be better to try a larger tank when first starting out.
*Edit: To address some of the questions about stocking, the numbers I have provided are very rough estimation and accumulation of various amounts of resources and personal experiences of others/myself when keeping. The number you can keep is not something that is set in stone when selecting your numbers for your sorority. It is something that may need further experimentation, and what I have provided can be a baseline in selecting your initial stock that should be flexible enough to allow changes, if the keeper deems fit.
Choosing Your Girls:
Arguably, the best part of a sorority is picking out your girls. There are some tips and tricks when selecting your stock that can help in reducing aggression. Firstly, go for the youngest Bettas you can find; the older ones tend to be more territorial and less social with tank mates. They are accustomed to living alone and tend to have more aggression when introduced to a sorority. Younger females are generally less aggressive, better at sorting out hierarchies and more flexible when accepting Betta tank mates. Growing up together help curb their aggression and conditions them into having neighbors. If you can, find young siblings, they are the the best option as siblings are born together and usually raised together when they are young. Additionally, select Bettas that are in close proximities of each other; this means that select Bettas whose cups (most of the time, it will be cups) are close to each other so that the girls can see each others' faces. This will reduce aggression as they are used to one another and there are no strangers going into the tank.
However, the most important port of sororities are the colors; I call it "color-compatibility." Bettas tend to challenge those of the same color as they are, and careful selection in different colors of Bettas should be made. A high contrast in color shades are fine, for example, if one is a darker green color and another is a more lighter, teal-green color, those are color-compatible. Or, depending on how many colors exist on a single Betta (i.e. having koi or distinctly multicolored Betta) should be okay as well. The only real issues arise when, for example, one is red and the other is a similar shade of red as well; it doesn't matter if the one red better has the tinge of blue along her fins, the other red Betta will not care. Anyhow, I think it is more fun and exciting to have your own rainbow swimming in your tank!
Be wary in your choices! Often, you may have chosen a male plakat by mistake and it can be a headache to fix the solution, and by then, it may be too late. Generally, females tend to have a rounder body shape and in light colored ones, you should also be able to make out the ovaries; they look like a small yellowish triangle behind the intestines. The male plakats will often have longer ventrals, a defined "beard", possibly a fuller caudal, and generally a sharper angle to the shape of their anal fin. Do not always rely on the eggspot/ovipositer method to determine gender. Young and older males may have what seems to be an eggspot while some males always have had what seems to be an eggspot. If you are really unsure of the gender, its better not to buy and be safe rather than sorry.
Introductions and Aggression:
Another important step, and the make-or-break of your sorority, is the introduction. Acclimate all your Bettas at the same time (this also allows them to look at each other for awhile and warm up to one another if you were not able to find some that were in the same proximity) and release them all at the same times. You'll ideally want to release them into the tank/all be in the tank within five minutes. Any considerable time between adding the fish and the Bettas may have had enough time to establish territory and may feel she has to defend herself against the others, hence more aggression. This is also the time to monitor to see if any girl is being too aggressive. Fighting will occur at first to establish the pecking order and should be nothing more than chasing and light nipping, but not fin tearing or severe bullying. If you notice a female being particularly aggressive, its best to remove her and keep her in a separate breeder (in the tank) where she can be in proximities of the others but not harm them. Separate for approximately 20 minutes and reintroduce her. If she continues not to be sociable, you can separate for a longer duration, up to a week (at the most). The idea behind this is to better condition her to tank mates so she will be less likely to attack when reintroduced. However, even after a prolonged separation she still continues to show extensive aggression, you should remove her entirely (see "The Back-up Plan" below). Make sure to monitor for at least a week. Once everything has settled down and the hierarchy is comfortably established without too much aggression, you are free to admire more and worry less.
The Back-up Plan:
Sometimes you will get a Betta that will not cooperate no matter what you do, and you find yourself removing her. In that case, make sure before hand that you are able to return her to the store or provide a separate, established/cycled tank for her. Depending on the policies of the store and especially if you purchased online, its best to have a separate tank around for this reason.
More Bettas Later:
If for, by some chance, your bettas do die, either by old age or another reason, or you want to add more females to make up for the loss and/or complete the group, there are a few things you should do. Firstly, I recommend adding more than one fish at the same time, this reduces overall aggression and bullying towards the new member. This is why I provided a flexible stocking number earlier; in the case one dies and you should add two or three, your number should have enough of a buffer to accommodate all of them. There are exceptions however. Some have been able to add a single female without any excessive bullying; they just have a very social tank. This will, of course, depend on how sociably flexible your female are towards a new member. Don't worry if some fighting occurs again, the pecking order usually needs to be reestablished with the introduction of a new member. Just ensure that too much fighting is occurring. You may also wish to acclimate her for much longer to allow the the Bettas to observe each other safely before rushing to release her, possibly inducing some unwanted aggression.
Another worry when having a sorority is feeding time. While you should provide a varied diet of frozen or freeze-dried, as well as different types of food, such as flake and pellet (more explanation below) and it can be quite difficult to ensure everyone is eating, and requires a little more work on your part. The most dominant females tend to cruise along the top and will be the greediest eaters, snatching everything up before the other have chance. A solution to this is to feed the dominant ones first, with floating food/pellets, and once distracted, provide the shier Bettas sinking pellets that they can safely find and consume on the bottom. Or, you can purchase (or DIY) floating feeding containers where you can place in multiple locations allowing multiple places for your Bettas to eat. Additionally, you may find it easier to condition your Bettas to accepting flake food (in addition to other foods) as well; flake food will travel to all levels of the tank and reach the different type of eaters and make feeding easier. You can also try training them to spot feed from forceps, or really any other tool where you can easily control where and whom the food is going to. Another method is separating the females, as in a breeder, and feeding them individually. This method will require a bit of time and wrangling, but it ensures that everyone is fed. You can also feed some vegetable matter once in awhile, like peas to help with boating and nutrition. Because Bettas are natural carnivores, they may not readily accept it unless you soak it in the garlic solutions or condition them to eat it.
Enjoy! (+Pros and Cons):
After all that hard work, you should be able to sit down and admire all you have done. Betta sororities are extremely fun and have so much personality to them. The colors are limitless and are a great way to start off with a colorful tank where you know stores will always have them. They are wonderful in that they have all the personality of males and can be a joy to keep, if successful. However, as in any set-up, they can be hard to get a sociable group and feeding may prove itself to be a bit of a challenge.
I hope this guide has been comprehensive enough to take all the guesswork out of owning a sorority and sparks interest in keeping this kind of tank. However, it is not soemthing a beginner should try. Those with intermediate or advanced fish experience and skills are recommend to owning this type. Especially with its increasing popularity nowadays, I think it is better to have a source of information that accurately describes the work involved, and have it all in once place. I will update if necessary and will appreciate any questions asked to help better streamline this guide. Any comments or questions are welcomed. This is my first article and any feedback or tips would be great to better improve any future articles I may plan to have. It was extremely fun to write and I appreciate you taking the time to read this, and I thank you for that. And, as always, I hope this helps and best of luck!