Thanks for admiring my fish, fff. Not many members liked him in the photo contests.
Actually, he's a "Copper," three translucent layers of color. Depending on the light intensity and angle, he can look copper-tarnish green, dull blue or (mostly) copper-penny brown. But he's so shiny I can't get a good picture of this color mode. He's a 4-ray HMPK and proud of it.
The light blue HM in my album was my dragon-scale---a devil-dragon because of his red fins. Some people consider dragons as only white. Some include light blue as dragons.
I keep my wild Smarigdina in a 2.5g bare-bottom tank. His Hagen Elite mini filter (set on low) has a little added foam, but not much. And just a few Anubias, so no real plant help. I vacuum and change 50% once a week (easy to keep a bare-bottom clean). I get 0.00ppm ammonia and nitrite and ~5.0ppm nitrate every week. One drop/gal Prime with the change just to chelate the heavy metals (My well has no chlorine nor ammonia).
I would say that any sponge filter, even a small one, is plenty for just a Betta. When I activate my 3.0gals, I run an ATI Mini sponge filter, which is way overkill.