[arin]

I have my Betta in a 1.5 gallon tank for now. He is Always flaring and chasing his reflection alot. i really don't want him to stress out too much. he is just getting over fin melt. Is there anything that i can do to reduce the reflection that he sees?

 

[Micho]

Put a black piece of paper against the tank walls outside of the tank.

He shouldn't be able to see himself anymore.

 

[Hallyx]

Apparently medium tones reflect less than black or white. And textured or pattern is even better.

 

[Twilight Storm]

Crafting felt sheets look nice too and get rid of the reflection problem.

 

[Hallyx]

I just tried a little experiment that you may want to try at home, just to see for yourself.

Dark backgrounds reflect the most.
White ones reflect less.
Cardboard brown reflect even less.

But the thing that reflects not-at-all is a background that does not touch the tank; even a half-inch of space between them when it's lit up by the tank or the room light. This is related to the following:

Everyone knows that a lighted tank in a dark room has reflective walls. So light up the room/background.