tibby25731
Fish Herder
Brilliant! Looking forward to seeing him later 
He doesn't seem to bothered by it, he's still pacing about and taking notice of me when I get close to the tank or walk by it. Hes actually watching me riiiiggghhtt now. Now that the filters calmed down and doesnt create so much water disturbance he seems alot happier.
Fin rot can be black too. Hard to decide on a fish of a dark colour whether it is funny coloured regrowth or fin rot! Just keep your water as clean as possible for a few days and see how he is - if it changes or gets worse then get some fin rot meds in there!
I can't remember which way stress lines are on bettas - horizontal or vertical! But it sounds to me like they could be stress lines, especially if they are fading now he is not getting battered by the current!