Fin got shredded overnight- Fin rot or fight?

[justinl]

I have a domino damsel that was fine last night when I went to bed. I always inspect my fish each night and I didn't notice any white spots or even a hint of fin degeneration.
6 Hours later I woke up to find that one of the pectoral fins was shredded about half way up the fin. I see no white specs or redness, and was wondering if Fin Rot could appear within 6 hours and cause such a drastic change or whether a more valid theory is that it got nipped by my hermit crab. There is only 1 other fish (a Blue Velvet Damsel) and they get along very well.
Any thoughts?

 

[pufferlover]

Seems like it was attacked by one of the 2 you mentioned. Very doubtful that it would get fin rot on one fin and have it show that fast. get some Kordons Poly Aqua which is a commercial grade conditioner and fin repairer it works great and fast. Available in 16 oz bottles at most lfs. Keep a eye on it tho and if it starts to turn red then you may need to medicate for bacteria infection.