hi! i decided to get into bettas after my dad told me they make good puppy-fish, but are small, unlike oscars.
first, a pair of females cannot work together. they need to be a trio or one girl will be bullied to death. a trio can live with a male, provided the tank is HEAVILY planted and the male isn't an agressive boy, passive or passive-aggressive otherwise the girls will definately be eaten. even passive boys will pick on girls though, so watch them carefully and only do this if you really know what you're doing, but either way the four fish could not live in a 5 gallon, so it's a moot point =)
bettas are a bit hardier and less picky than some fish, but are still fish. some plants (silk or live, no plastic to tear those pretty fins!) light, unless the room is very bright (never put a tank in front of a window) gravel to hold the plants down and grow nice, ammonia-eating bacteria, hidey-things are a good idea. bettas like caves, just don't get a small pot with a hole in the bottom, it may look tiny but a betta can fit there, i learned that the hard way and lost a boy (rip mack) heaters... hmm, my boy gets on fine without one, but he's surrounded by heat-holding plush toys in a smoldering hot room. during winter i'd definately suggest a reptile heating pad to keep his fishie-tootsies toasty warm, or a 15w/25w heater for anything above a 2.5g. filters, most people say a small tank can't be properly cycled, but i have a filter just in case. it seems to cut down the ammonia a little and cuts my tank changes in half, as well as clearing the debris away and giving the betta a nice current, which my boys seem to love. but, a betta can survive happily in a gallon tank with some silk plants and gravel, even without all their fittings =)
you *must* condition the water. unless you've got unchlorinated well water you must do that. i'm lucky, i get my water from an underground lake and it's filtered mercilessly, so no conditioning. bettas are individual fish, some may love light, others may want to hide away.
water changes! ah, the most difficult task of betta-ownership. first, i suggest a nice cup, a small jar or, if possible, one of those awful betta-hexes. take some tank water into the jar/cup/hex and net the betta into it. take the tank to a sink where the drain can be CLOSED and pour the water out. gather up fallen rocks and put them back, drain the water. wash the gravel thoroughly, wash any plants, rinse the filter. put everything back together and bring it upstairs. add as many quarts of water as the tank can hold; 3/4 cold, 1/4 hot. let it even out to the hex temperature, then add a bit of water into the hex. after a few minutes add the betta into his clean home. i think it takes less time for a betta to get used to new water that he knows then new water that he doesn't know.
and it's good youre asking, so many people buy bettas and keep them in jars or cup or
good heavens, peace lily vases