Hungry,
Believe me, the barracks thing still scares the bejesus out of me too.... BUT I WANT ONE (I digress)
Something about the 22 litre mark is actually perfecto for a spawn tank (you'll need one down the track, mwahahaha - but is very big for hospital.....)
These Aqua Ones come up lots second hand on the Bay, so don't buy a new one!
I find they're a good sorority tank too, but the filtration really needs to be altered, they have a craaaazy spray-bar and it's really too much for betta - they're used to still water or really gentle flow.
I have to admit - there are some super cheap tanks at places like Kmart / big W that are anywhere from 12-22 litres, and they're pretty good.
The filtration is weak as, so it's actually suitable, and you just need to pop a heater in there and bobs your aunty.
With this whole tank / intro to betta thing it might be worth mentioning water.
Sounds silly, but I have to say, I've learnt LOTS about water, mostly because I was coming up with so many health issues with my fish.
Git yourself a PH test kit - it's handy to know what PH the water is that comes out of your tank... so if you need to buffer it or not.
Betta like a stable PH, and are kinda flex about what they need, so long as it's stable.
My PH is pretty useless (5.5) so I use CARBONATE HARDNESS POWDER / BUFFER this keeps the hardness of the water stable, and the ph stable at 7 - it's a little investment for big piece of mind (don't never use ph up or down, they don't FIX the water)
Also - you might want to look at a little bit of shell grit, and aquarium salt - it's the first thing to throw at an ill-looking fish, mineral rich water helps fish keep their minerals IN - mineral deficient water leaches the minerals out of the fish = sick fish.
Another good thing to have on the shelf is Bettafix - it's got lots of goodies to help them put a bit of pep in their step if they're looking a bit flat.
And Stress Coat - it's a must! Dechorlinates and treats water to make it fish safe... there is so much junk in council water, it's not funny.
So when i add new water, it's got:
Same temperature as whats in the tank! 24-26 degreez
Carbonate hardness powder (GHz)
Tiny bit of aquarium salt
Stress coat/dechlorinator
When you're establishing the big tank with filtration etc - do a bit of research on CYCLING your tank... there's a few threads on here too that might help.
It's a little shopping list, but believe me - you'll save in the long run with sick fish and fatalities (learn from my mistakes!)
End of rant!
-ProNess