Here's a little update, the Betta now has his own little tank (2.5g) with a sponge filter that sits on my window sill. I moved him because he was nipping at all the little tetras and getting bullied himself by my pair of rams in my planted tank. He's very happy in there and likes to watch everything go on outside (first pic). I got him to flare his fins by holding up a mirror to the side of the tank (second pic). Enjoy!