you can really only do the betta and snails or shrimp. most other kinds of fish needs more space because they need to be in schools/shoals, or they just have a massive bioload.
some bettas don't do well with companions. they might think your shrimp are a snack, or your snail's antennae are yummy worms. you really have to experiment and know things can go wrong. when i added my rabbit snail to my 3 gallon, i was convinced at first Swish was going to eat her antennae. eventually he got used to her and they lived pretty peacefully together. then i moved the snail into the 29 gallon because dang, that thing can POOP. anyways, sorry for the side track ^^; a snail or two, or maybe a few shrimp is about all you can add to your five gallon.
you should buy a ten gallon if you want to add more fish :K
If you want snails I would go with a Nerite snail, they're smaller and have smaller bioloads than Apple/Mystery snails. Plus Ramshorn snails eat plants, no thanks. Nerite snails also can't breed in freshwater so you'll always just have one. :)
They feed off of algae mostly, so they'll do a better job of cleaning algae if you have any. Also pick up some algae wafers to feed your snail, be sure not to overfeed on algae wafer, supplement with blanching some spinach or zucchini, for that extra calcium to keep his shell extra tough!
If you want shrimps, that's a hit and miss. Most likely your Betta will kill them, so try to get cover for them, like some type of moss, or some hiding places. Ghost shrimps are scavengers they'll eat anything, leftover fish food, algae, etc. They're really cheap compared to other shrimps so I suggest them. Also with shrimps is that they molt, and during that them they're extreme vulnerable, a little poke from your fish could easily kill them. Supplement their diet with blanched vegetables too, spinach, zucchini, high in calcium stuff.
Also, no to the bristlenose pleco. They grow huge and you'll need a 20g minimum to house them.
Hope that helps.
Zebra Snails are actually just a colour pattern of a Nerite Snail. I have one in a 5 gallon with my male betta. They get on fine. :)
Snails or shrimp only.
Pleckos get to large.
Snails; I'd need to get an algae wafers.
Shrimp; may be attacked by my betta, but will eat left over food supplemented with zuccini, ghost ones are cheapest
Anything important I missed?
My plan, and hoping this works:
2 Herite Snails (maybe Zebra)
1 Ghost Shrimp (should I get 2?)
Well, I went to Petsmart today and picked up 4 shrimp and a snail.
Unfortunately, one of the shrimp wasn't playing it smart so Kevin killed him. I figured as much, but I still feel bad. Two of the other three are pretty big so they seem to be good at avoiding him and at least not flitting around in the mid tank like the one that got killed. I can't seem to find the third at the moment. The snail hasn't moved, at least not that i've seen.
ALSO interesting; I picked up two new bettas *headdesk*. Barnacles. Ah well. They are beautiful; a male HM and a female that I have no clue what she is. I think HM or P or both haha.
Obviously the new bettas are in their own little quarantine containers. The female didn't look too good at first, she was kinda head downing, but now she's better :D