Try, for the love of god to convince your manager NOT to give goldfish for those tanks. Not even ONE.
By keeping the betta in a 1 gallon tank you are basically replicating a puddle of death. Presuming your usual types of customers are the sorts I'm thinking of, they are looking for something easy to look after in terms of tank and fish yes? Well a goldfish in a 5 gal and a betta in a 1 gal is the complete and utter opposite of that aim. The smaller tha tank, the harder it is to keep stable and safe for the fish due to ammonia build up and lack of swimming space . So the store's current offer is completely useless for the needs of the customer.
Explain that the 5 gallon tanks are perfect for the
BETTAS ( one male only for the tank ) , and offer some sort of possible discount on the fish when buying a tank.
Explain that bettas absolutely do NOT live their lives permanently in puddles and hoofprints in the wild ( often a reason people give for keeping them incorrectly in tiny containers ) . Many thousands die in them as they dry up in the dry season. The lucky ones who manage to end up in slightly deeper ruts and pools use their labyrinth organ
as a survival method only.
Being able to breathe atmospheric air as a means of trying desperately to stay alive is not a reason to keep a betta in a tiny stagnant tub,
and it does not make them magically immune to the ammonia produced in their waste the same as all fish.
They need space, and they need a
gentle filter.
A properly cared for heated and filtered five gallon will give a longer living, much happier fish, and will not take up more than 14 inches of space if the tank is square or rectangular so it's hardly a vast tank taking up loads of room.
As for the one gallon tanks, why not convince the store to sell them as easy shrimp or sea monkey setups? They are fine for that, and cherry shrimp do not require a heater. They produce very little waste and can get by with water changes twice a week if the 1 gal has no filter.
The smallest I would *ever* recommend for a Betta is 2-gallons. Sure, 5 works, too, but.... yeahs. In my sister's room, at first, I had a teeny little 2-gallon bowl without a filter. Well, it would stink after two days! So, eventually, we got a sponge filter for it. Which worked wonders, btw.

Then, we cleaned out the 2.5-gallon that we had been using for holding drawing stuffs just recently, and placed the female in there; I planted it up, and put her filter in, and she's happy as anything!

The only problem is, the room is so cold, that even *though* the tank's heater (100 watts or something.... probably just 10 but Idk XD it's rated for 2 - 15 gallons ^^;

) is rated for 79*F, it's only around 73*F.

Ah, wells. ^^;
Some people say that 2.5-gallons, even *WITH* a heater and filter, will still build up poisons quickly; well, peoples who say that (not you two.... somebody else), let me tell you, that if the filter in the 2.5-gallon is all established and working properly, and if it's rated for like 5 gallons or whatever, then, wells, it'll still work the same! ^^;
Oh, and.... Also!!!! My friend who keeps her Bettas in tiny little bowls, when I told her that Bettas need a heater and a larger tank, she went all like, "Oh, but they LIKE small spaces!! They're coldwater fish!!" Couldn't be farther from the truth, I knew, since I had been exploring on the Web for a while, but.... Well, you knows. :roll:

Now, I think that she's *finally* starting to listen to me, but.... Well, her poor Betta fish!

She only has, like, 3 left; yet, she is waiting until they die to do everything right.

It's dismaying, and I may adopt them off of her *someday*, but, right now.... I'm kinda broke, so.... What can you do with a person like that? Tell me, hmm?

I don't think you even *KNOW* how many times I've told her that she's wrong, and she didn't listen.... Hmms.... *ticks off on fingers* First, with the Bettas, when I told her that she wasn't taking care of them right; second, with her 10-gallon tank & the goldfish & gourami in while cycling, when I told her that that wouldn't work.... etc. Now she has two goldfish in there!!

Well, anyways; I'll stop ranting about my friend, nows; even though she *doesn't* do quite well in some things, I think she'll learn over time; and besides, she can still be a good person. ^^;
Just a note Honeythorn, although the labyrinth organ originally evolved as a means of survival there are plenty of bettas that rely on it now. Odd to think you can drown a fish, but I'm sure you've seen times when they've been trapped under the water and unable to get to the surface have died.
Totally.

I just had a female Betta die on me yesterday, and her head was buried in the rocks.

I woke up and found her that way; I didn't test the water that day but tomorrow is my water change day ('cause I missed mine on Sunday), and the cories certainly seem fine.... Well, I hope so; they've been going up to the top, so I may test today. But anyways, yeah; if a Betta fish gets trapped at the bottom of the bottom of the tank somewhere somehow they will die; I've seen it all happen.

Not very nice.
Yes which is why I detest the Fluval edge so much if used
as advertised (full to the roof) and used as a betta home in particular . Utter madness.
But either way having a labyrinth organ does not make bettas immune to their own ammonia and nitrites.
Which is why they need a filter like all other tropical fish. So many times I've seen/heard people state that " they don't need a filter because they can breathe air"

Breathing air has nowt to do with
anything as far as waste is concerned. As long as you have airspace between water surface and the splash tray or hood ( which you should ) then there should be no issue with air access for a betta.
Yeah, I mean; if Bettas were magically immune to their own ammonia and nitrites, then, lessee, how did my female Betta in my 10-gallon tank die of a cycling tank?!

This was way before I knew anything about cycling, mind yous.... The guy at the pet store was just all like, "Oh, yeah; leave the filter alone for a little while, and, TA-DA!!!! Add fish in right away; it will be fine."
Oh, how wrong they were!
Yeah, but, then, I got the informations. ^^; My friend, who keeps her Bettas in tiny little bowls, she just went all like, "Oh, it didn't work 'cuz you had female Bettas together." Which had absolutely *NOTHING* to do with it, btw. But, whatevers. ^^; Idk. She's just.... the type of person who wants what she wants and she won't be told otherwise. That's all. ^^;
Totally, I certainly wouldn't disagree with that!
Ammonia poisoning does serious damage. Starting on the more suceptible tissues such as gills and following on to remove slime coats and burn fins.
Not pretty to see
Ammonia poisoning is absolutely terrible. Just.... *terrible*.
Well, anyways; that was just my little spiel. Feel free to analyze and enjoy.
