Betta seems ill?

Question
QUESTION: Hi,
I recently had a problem where my heater in my 20L tank blew up due to a power surge so I didn't want to risk chemicals leaching into the water. Because of this I had to move my betta into a cycling 54L tank with an ammonia nutraliser and he was much more active in there. I moved him back into the 20L as the tank can't cycle with the nutraliser in it. The water I used was shower water, as it has the least trace of ammonia in it. I let the water sit for a day, added my water conditioner and ammonia detoxifier and the water chemistry is great. I noticed a day after I moved him, which was yesterday that he isn't moving and is resting for the whole day. He is eating normally, but is acting very odd that it is worrying me. Could this settle down as I just moved him in a new tank? (I did let him get used to the new tank water for 15mins before putting him in) or could this be something bad? I know it is nearly impossible to diagnose through email but I thought that you might know from owning bettas?

thank you for the help

ANSWER: Alexander,
It is most likely stress from being moved so much. Just make sure his water is at 80 degrees. Just leave him be for a couple of days and he should be ok. Let me know if things change for the worse.

---------- FOLLOW-UP ----------

QUESTION: Thanks for the answer,
So far so good, he is swimming and acting a lot better, not 100% but I am sure he will get there in a few days. He isn't yet displaying his fins all the time, only sometimes but that will hopefully start soon!

It's amazing how something so simple as changing filter wool can cause such trouble! Luckily now I know not to do so!

As I need a filter for the 54L tank I am cycling at the moment, I was wondering if you know how to go about replacing filter wool without loosing all of the bacteria? ( I have found out that the wool holds around 90% of it)

Answer
Alexander,
Glad he is doing better. You do not him to flare all the time. If he does, then he is stressed. You want him to have all the fins and his tail down and not displaying. He only does that if he is defending himself or his territory or if he is breeding. Sometimes males will flare if he sees another Betta or if he sees his reflection in the glass. The best way to clean the filter is during a water change. Rinse the filter media in the water you took out of his tank. That way, you keep the beneficial bacteria.