Betta And Small Danios. Other good tank mates for bettas include plants, like java fern or anubias , as they will provide cover and oxygen for the fish. Zebra danios are another popular betta tank mate.
They do have a bit of an issue when it comes to compatibility with tank mates, however. The first day of adding them, the betta chased the danios nipping their tails for about an hour, but, the tank was big enough and with so many dense old growth plants (some of the plants had been in the tank 10+ years and are huge), that before long (within the first 2 hours of being added to the tank) the betta established one clump of plants in the corner as his territory, and never left that. Celestial pearl danios prefer water with a ph range of between 6.5 and 7.5 and a soft to medium water hardness of between 2 to 10 dkh., in comparison, betta fish need a ph between 6.5 to 7.5 and a water hardness of between 3 and 5 dkh.