Stresses Betta

My 55gl tank completed the cycle 5 weeks ago and is stocked with 3 BN Plecos, 5 Cories, 1 Betta and 11 Neons.
All was good and peaceful until we put a background to the tank. Yesterday the Betta was flaring like crazy, and this morning as well. We dimmed the light, but this dod not help.The tank seems to have a lot of reflection.
I now moved him to a 5gl tank by himself.
Is there a difference in tank glass that is more or less reflective?
He is not happy in his new tank neither, but at least he is not flaring anymore. He definitely has not as much swimming space and plant cover.

 

This site seems to have some good general info.

Betta Fish Flaring (Why They Do It And Is It Bad?) - Betta Care Fish Guide

 

Interesting article....and I think I found a solution. I will build a moss wall to hide the glass on two areas. See how that will work
It will be some time before he can move back. Fish happiness above anything else

 

Update....he seems to be happy in the 5gl QA tank all by himself, mellow as can be and eating without issues. I will most likely get him into a 10gl aquascape I am building right now. Just put a sponge filter into my canister for seeding, see how that works out.

 

Fast forward, the 10gl did not work out.
The Betta did not have an issue, I just did not like it.
So four weeks ago he moved into a 20gl tank, and he seems to like his new Bettadom. He seems happy, I am happy, life is good.