Just a question about finrot

[Whiskerz]

I've been looking through the forum and i see that some ppl's betta's have finrot, I have 7 bettas and ive none of them have had it before.
What causes finrot?

 

[Synastic]

I have had bettas get Finrot, the reason for them getting fin rot was because they had ich (ich another diease). I think it can be caused by poor water conditions or the betta is under stress, but I think the main one is poor water.