I recently purchased a group of betta imbellis and thought that I should write down the differences I've noticed before I get used to them and forget.
For the general info on the species, the IBC has a great page
on betta imbellis. The page has information on where they're from, water parameters, and basic breeding info.
The things I've noticed:
1.) If you can keep betta splendens, you can keep betta imbellis. I have them in the exact same water at the exact same temperature as my tank with the two male splendens (divided, of course) and they're doing very well. They eat the same types of foods and everything. More frozen/live for the wild crew, as they're still getting used to life in a tank.
2.) They're little! Without the extravagant fins of their splendens cousins, these guys look surprisingly tiny when they show up. They get up to 2" in size, so don't expect anything big or beefy. These guys are slender.
3.) Yes, the websites are right, they can be kept in a group. I have eight currently, and my latest guess is three males and five females. I'm still guessing on some of them since they're young and have to color up from the trip across the country. This is a good ratio, to keep the pressure off of individual females. You don't want a bunch of males in together.
No, they are not a 'schooling' species. They are still bettas and the males are territorial. They need space to spread out. I have my eight in a very heavily planted 40g breeder.
While the girls will hang out together, the boys prefer to stake out some space of their own. The plus side is that they really are the peaceful bettas. When they have an argument, it's some flaring and possibly some chasing. Not a lot of nipping and certainly no locking on and rolling behaviors. For a ten gallon, you'd only want 1 male and a female or two, you'll need a pretty big tank for more than one male in together. Things are pretty peaceful with 3 males in the 40g breeder and a million hiding spots.
4.) These fish are just as smart as their splendens cousins if not smarter. My group was wild caught and in the week I've had them, they take their daphnia from a dropper and their blood worms from the turkey baster. They know the drill. Feeding time is great fun since they swarm together as a group to nab whatever I'm dropping into the tank. They were disgruntled when it turned out to be an algae wafer for the pleco. They will also snatch sinking pellets and take off with them like little bulldogs, so watch out for that.
5.) Tankmates. Yes to cory catfish, my imbellis practically school with them. Both species pick at the sinking pellets I feed to the cories without any trouble. It makes a neat image with the albino cories and the nearly black imbellis. The BN pleco, they don't seem to notice it exists. The snails? Nope, not a good idea. Antennae were gone in no time, and these were my good sized apple snails. They're bigger than the betta imbellis. The bettas just don't care. The snails have learned to take cover and the antennae are coming back, but not recommended. Also would not recommend any kind of shrimp, unless the plan is to feed them to the imbellis. These guys are serious hunters and in my experience, faster than their cousins with the heavy fins.
6.) These are not splendens. As my husband announced when they arrived 'did you get minnows?'. These guys aren't nearly as flashy. If you're looking for a glittering collection of fish, get some fancy guppies. The females in particular are brown with just hints of color. The males, though, do color up beautifully.
This is one of my males, taken from my own tank with no fancy photography (obviously):
Please excuse the line of algae, the support crew has since cleaned that up. By comparison, here are some of the girls:
If you're looking for a lot of dramatic colors, not the species for you. If you like the idea of keeping a small group together and seeing them interacting, then these guys are great. They're very charming, intelligent fish with plenty of personality. I personally think they look very elegant. They make for a great addition to a heavily planted tank and look fabulous zig zagging through tall plants.
I'll try to keep this updated as I learn more about this group. I think I just spotted one of the males attempting to convince one of the ladies to join him by his bubble nest, so I might even have commentary on spawning soon!