I was asked in private message about how to teach betta girls their names.
In the store, since I'm looking for social fish, I test all the girls I'm interested in by seeing if they recognize me as a creature to interact with. If I get ignored I put them back on the shelf and come back to them later on. We're looking for pets, not ornaments. Most any girl will come around but if you're looking for sorority girls you want the "geisha" who not only responds to your presence but is interested in it. If the people around you respond to your fish-attention before the fish does... she's probably not a keeper. Remember that we're not looking for the feeding response: following your hand looking for food. If you've never seen that just walk along the tops of tanks at PetSupermarket wiggling your hand.
First there are some considerations about using names with fish, some of it is a little tricky as most people don't have experience with hearing voices through an air-water-air interface. That comes from bathtubs or wearing ear-plugs in swimming pools. Some of it makes simple sense.
Each name should have a different tone or cadence, so "blue" and "two" and "true" "zoo" "goo" all will likely sound the same. We're using the labyrinth gland in their head for resonance.
I commonly call the girls after their colors and try to only have one color of each (not only so I don't confuse/insult them, but because some girls like being unique).
So you've got a plan of having six to ten girls in your tank and you go out and find em all.
First thing I always do when I bring a girl home is see how aggressive they are by letting Goat or Fluffy, my bull males, meet them through their tank walls. I sit them down within the spreading light from the boy's tanks. Sometimes I show them both. (A girl who flares at the boys and ignores them is going to be aggressive. You'll need to be assertive with them so they know you're the big fish.)
Then I feed them what they'll be eating IN THEIR CUP so its clear I expect them to eat it.
Then I teach them that my fingers are my fins. Wavy wiggle when I talk to them, "little fish, hello little, pretty pretty" etc. When I talk I wiggle.
When I say their name I point at them. Its pretty much iteration at this point. When you get their attention say their name and touch the cup, not hard or tapping. They can hear just the gentle touch.
When its time to put them in the tank just stick them in and let them swim around. Watch them and call the other ones away, when you scold the others for things point-touch the tank and call their names.
Get the new girl's attention when they're alone with the touch and wiggle and call their name. You can't whisper it, use your puppy-calling voice.
I like to start off in the cup then call and check each girl about three times a day. Betta are still fish and can unlearn to make room for other important stuff.
When starting up a sorority its best to spend a lot of time calling them over in their own cups. I've found that most girls will learn their name within a week even when you put them in the sorority after just the minimum feeding.
Clear bright names are best. Keep in mind your smarter girls will be confused if you immediately get a new blue girl and call her "blue". So short names are best. Emerald I called "emmy" I had a "bluetoo" with "blue" at the same time.
This all works because betta have the labyrinth gland, they can feel thumps from far away. Commonly they show the prey reflex if you drop something scary in their tank... that diving to a corner and acting dead move. My boys right now are Fluffy, Littleboy, Goat, Splotch, Glee and girls are Sunrise, Pink, Silver, Cotton. I have a molly male, Buck, who comes to any noise but couldn't tell Hassenpheffer from Chu in a sound test. One female guppy named Splittail who knows its her name. I spent a lot of time caring for her to grow her up from a runt in the tank on my desk, she probably got 10x the normal betta talkings.
More than their names most my girls learn my finger talk. Its fairly straightforward.
To "swim past" and let them know I'm around I wave my fingertips (like tapping wave motion) by the front of the tank and say "hey girls".
To call for feeding time I give a gentle tap of the food jar on the table, this is because I normally have other fish in the tank (tetra, guppy, molly) and its universal, but usually one or two girls will see me go to tap the jar and they'll shoot to the surface.
To scold I follow a girl around the tank with my finger and gently spread my fingertip against the glass. This mimics the flare spread of a girl quite well by ratio. So I'll chase them wherever they go and make flare-like at them.
To call one specifically I'll tap the glass with a nail, very gently, and call their name and wiggle the single finger.
One of the hand motions the girls can usually mimic is the cupping hand wave, where you fold your fingers up and down like you would at a child for bye-bye. The girls can bring their tail around and spread-close-spread-close it at you. When I think a girl is watching me I'll give her the little wave and see if she responds then call her name and "glass pet" if she does.
They can always see their own reflection in the glass, even if its coated with slime they're aware of it. You can reach up with the lightest touch on the glass and pet their reflection! Some girls just play at you but others will hold still and watch it.
Mirrors are great for girls, especially if you can call one over by wiggle or name and then show them their reflection in the mirror. Most of the time they'll realize its the same as the glass but clearer.
When the girl first realizes they can see their own reflection very often they'll do a little "startle" move, all fins out but not flared with the tight-fast station keeping wiggles on the side fins.
I've often used the mirror to re-enforce names. I've also used my digital camera.
The fun thing about this is the boys can be treated the same but they're harder to get to see their own reflection. Instincts get in the way. I usually do it by exposing the boys to the mirror several times a day. Goat likes to sit and look at himself! I assume that some introspection occurs because he doesn't actually threat-flare at the mirror anymore unless he's already angry.
I don't see learning a name or knowing their reflection as mandatory in the tank but they're both interactions we can share with them and the combination seems to give them identity beyond simply an intelligent pet fish.
The one problem I've run into with all this is when I've got two girls of the same color who both know their own mirror image sometimes they get pecking-order confusion. I HAVE had older girls attack younger girls simply because the older girl knows their own reflection and the younger is same colors. Don't know if its anger at a rival or some kind of insanity towards a mirror image that doesn't follow the rules...
So use mirrors with the girls, let it set there for hours at a time, won't hurt them. If you watch closely you'll see them realize and pose at it.
If none of this makes sense its the really nasty flu going round down here.