*Warning* Female bettas are great fish; however, they can be just as temperamental as their male counter part. I have had both experiences and watched one little female destroy a small group of neons, as well as another female betta (both bettas were in a 50 gallon tank, which goes against the rule, "if there's enough room, they will avoid each other"). One member of this site used to have three female bettas (I know the tank was bigger than a 20) and they got along fabulously. Unfortunately, she lost them all to disease and when she restocked, her new bettas did not get along and I believe she had to set up individual tanks. That's my warning on female bettas.
I have kept two types of shell dwellers over the years and must say you would be missing out. Their behaviors are wonderful, they make great parents and who could resist fish living in shells?!? My
N multies, with a max size of 1-2 inches, are currently raising two broods of fry and it's interesting to watch them pick on the pleco when he gets near. I have had the parents for almost two years and honestly, they are among my favorite fish. My husband and I had to downgrade the number of tanks we had from 13 to 3 due to two long distance moves and a baby on the way. There was never a question as to whether the shellies would stay with us or be sold at auction—the female bettas were sold, but not the shellies. Here's a pic of my shellies with Texas Holey Rock and of course--shells!
If you like larger fish, try
N. ocellatus, which are a bit bigger and IMO, more aggressive. Let me rephrase that, they are aggressive when raising fry--they would outright attack your hand if it was in the tank! The first pic is a female and the second is of the male. These fish are amazing substrate movers.
