I'm worried I did something wrong

[Waterfins]

I just got my crowntail betta and placed him in his heated 2.5 gallon tank after acclimating him to the water. I set this aquarium up weeks before and tested the water, the PH was 7.0 and the temperature stays around 25 degrees Celsius. I also added some bacteria supplement. After a few days he started itching on decorations in the aquarium. I added some AQ salt and the symptoms seemed to clear. But right now he isn't at his normal activity level which worries me. He's not laying and gasping for air or anything but when I got him he swam around with energy and now he just kind of trudges along. I'm really worried I hurt him or something, I'm so scared...

 

[Essjay]

Have you tested the tank for ammonia and nitrite? You mentioned adding a bacterial supplement but these don't always work, and they also need added ammonia to feed any bacteria from the bottle.
Testing the water before adding fish will show perfect water. You need to test it now.

 

[Waterfins]

Have you tested the tank for ammonia and nitrite? You mentioned adding a bacterial supplement but these don't always work, and they also need added ammonia to feed any bacteria from the bottle.
Testing the water before adding fish will show perfect water. You need to test it now.

The Nitrite is at 0 ppm, the ammonia is at 0.25 ppm and the nitrate is at 0 ppm

 

[nessar]

You need to keep ammonia at 0, so you'll need to do plenty of partial water changes as, if you have a filter, your tank is in the middle of a 'fish-in-cycle'. There is more info on this in the beginner's section of the forum.
If you don't have a filter, then you'll need to get one, or you'll need to do water changes every couple of days forever to keep your fish healthy.
Whilst you're in the middle of establishing your bacteria cycle in the tank, it's best to keep feeding to a minimum to limit the amount of waste, and remove any uneaten food after feeding. I tend to do it every other day. If you can get filter media from an established tank, that will really speed up your cycle