Most people say Cories need to be in a school of 4 or more, but I find that 1 or 2 will work fine. I used to have 2 of the Green/Bronze variety in my 10 gallon community with my mellow Betta Milo, but have since then transferred them to my 20 gallon high.
A better choice for the smallness of a 10 gallon would be 3-4, or even 5 of the Otocinclus catfish, they're pretty small and sensitive fish, so you need to be sure the tank is mature enough (Has been running for around 6 months or more) but I put just one in my 10 gallon Betta tank when it less than a month old, and everything is fine, just luck I assume.
If you want something that will swim in the top or middle section of your tank and doesn't really stay on the bottom, you'll need a fish that 1. Isn't aggressive, 2. Not be a fin nipper and nip the Bettas beautiful long fins, and 3. Not have a flashy or long-tail the Betta may be interested in nipping or attacking the other fish in case they mistake it for another Betta fish.
You also don't want a big school of fish as that may stress the Betta fish, Neon and Ember Tetras are pretty good and stay within these guidelines, they also like to school, so you'll need about 5-6 of them.
Harlequin Rasboras are good and like to school/shoal in numbers of 5-6 and would fit nicely in a 10 gallon.
But just in case, make sure the store you purchase them from will allow you to return the fish if it doesn't work out well.
Note: There's a lot of controversy about schooling/shoaling fish. I think the standard is "add more until there is no change in behavior" and while a small school of 6-8 might not be bad, I know some people wouldn't call it good either.
Thank you for all the info, I've had a look and am thinking the ember tetra or harlequin raspbora I'll see what the shop have!
Well Known Member
More than 10 years
I wouldn't put Harlequin Rasboras in a ten gallon tank. I have 7 and they are all over my bigger tank. Just my opinion.
I have a 5.5 Betta tank with 5 ember tetras and an otocinclus and they all get along fine. It's also heavily planted and he is not the most majestic swimmer so there is no way he's catching anyone .. Aside from bugging the otto cat once in a while cause my betta thinks thats "his" piece of glass
I tossed 3 Zebra Danios in with my betta a week ago. They annoyed him a little at first, but he discovered they have good sense of self preservation, and will zip away if he looks at them.
He has taken to slow-motion stalking them.. he'll just float over next to them, then flare his fins, and scatter the tinys. They all seemed to bond over a feast of danio eggs on day 2. Now that they're in a bigger tank, he's chased them a little, but overall seems uninterested in deadly pursuit.
Shorter version: start out by adding a few small, quick fish that don't have a reputation for nipping find. If that goes well, try a few more. If not, have a tank ready to isolate whomever is being rude.