I'm almost 98% sure it's fin rot.

[ANHEL123]

I am glad he is better. For 2.5 gall actually you always need to do 1-50 and 1-100% water changes a week. Some people even recommend 2-50% and 1-100% a week.
If you would have light 24/7 it will definitely stress him out.

I am confused that you wrote taht he has that with goldy sheen cover or color on him when you shine the light. Is it something new or he was like that when you bought him?

The reason why i recommended to raise the temp because temperature over 85* will help to speed up parasites (velvet)life cycle and they will fall faster and some even said that temp over 85* will even kill them. So i am wondering if he really has velvet and the water changes and temp raised helped.
Temp 76* will never make betta lethargic. So the fact that he was lethargic means that something was wrong. Usually bettas pretty active not laying on the bottom. My bettas actually live in 76* and some even in 74*. So really it not the temp that made him lethargic before.
So if that color that you talking about is new and i actually can not see it on the picture what i would do is raise the temperature as much as you can and do aquarium salt with daily 100% water changes.
Just like Sakura wrote : ''The salt will help balance his electrolyte level and encourage the production of slime coat, which will in turn help protect him from infection and infestation of parasites''.

And if that color you talking about is new then i would even increase the aq salt dose up to 2 tsp/gall with daily water changes. Unless it just his natural color and he had it before then just water changes will help.

[Sakura8]

Does the gold sheen look like this?


Or does it look like this?


If it looks like the second image, that is natural iridescence and nothing to worry about.

[resh2rei]

hi guys!

What i'm talking about is in the picture attached. I think anything that was wrong with him before was just getting adjusted to the new environment - i've only had him for less than 5 days. It looks like the second picture, a bit...
And i dont keep the light on 24/7 I turn it off in the night and the temp is usually almost the same when I wake up.

Thanks mogwai, I'll try to find that heater! :D

[ChoclateBetta]

I dont see anything unhealthy.

[ANHEL123]

Yes if it what you meant then it his normal coloration. I thought that you wrote all over his body. If it only that Oh i am glad!!! But make sure you do 1-50 and 1-100% water changes a week. Or 2-50 and 1-100% a week.

[ChoclateBetta]

I think the OP said they do that.

[Sakura8]

resh, the iridescence you see is normal. :)

[ChoclateBetta]

I am suspicas my sisters new betta is sick so I added aquarium salt.