Betta Fish: Is my betta boy healthy?

Hes obviously gained more colour since I got him.

I got him almost 3 months ago.

Hes always active and running for food whenever I feed him, I feed him twice a week with 6 small betta flakes.

I've noticed his fins are not the same when I got him, they look a bit shredded but I see no sign of stress or him losing his abilities or his active pattern hasn't changed, he's not lazy at all.

He has no tank mates other than bladder snails and blue shrimps and some malaysian trumpets and I also run a dirted tank do there is a reasonable amount of algae.

Can someone please help me identify what's wrong then? I don't have any aquarium test kits or so, I only top up with new water every 2 weeks. The tank as a whole is 4 months old and everything is fine in the tank visually and his other tank mates are normal and thriving.