7 is a good number but you could also add a few other small shoals of something like Ember Tetra, White Clouds, zebra Danios, and so on that would in shoals of 6 and a heavily planted tank be very flashy. You could add a shoal of Cory after the tank is established and cycled also.
This being said you need to have the tank overly filtered, so the Bio Load is cared for properly and the tank stays crystal clear.
RussellTheShihTzu and I both agree they are underrated fish for a community tank. I just finished a 10 gallon community and I took Russell's advice on the stocking and I started the community off with 6 Ember Tetra and my newest male betta Cal. He is a beautiful blue Half Moon with giant genes. his body size alone is 2.5 inches and he is still growing. I also added 6 White Cloud and 6 Zebra Danios. I finished the tank stocking off with 6 Cory cats 3 panda Cory, 1 Sterba's Cory, and 2 spotted Cory. This tank is heavily planted and I love the activity in it. I have changed the filter from an Aqueon 10 LED to an Aqueon 20 LED which gives me almost double the GPH in filtration.I did have to reduce the output flow but I did it with African Water fern and money wort. there is still a current for all the other fish and with the position of the plants there are a few spots that have no current so Cal is able to eat with out having to chase his food all over the tank.