Sorry about the bad quality of the picture. I can add more plants. There is one corner completely covered in plants but I’m waiting for them to grow some more since the tank is pretty new. I didn’t get the whole tank in the photo.
It looks kind of like the tank of another member but that was not on purpose. I did use the same method for a pre intake filter though.
Ember Tetras would be great! They stay nice and small and should be fine with a betta.
Depending on the length of the tank, Harlequin Rasbora should work as well. I obviously wouldn't get as many as the Ember tetras as they are larger, but still I've kept them with a betta in a 10 gallon before with no issues. Though I now have a new one who seems to be a bit of a jerk, so I guess it depends on the fish. Though typically it should be a fine combo.