Yeah it seems like that tear is from flaring too much. :)
Hehe, cheeky little boys flaring at each other. Yes putting a barrier in between the tanks will stop them from flaring, it should heal up in no time in clean warm water.
A paper folder would work.
But finrot can start as pinholes, and so can ammonia poisoning. So I suggest doing a water parameters test, for ammonia, nitrites, and nitrates, just for safe measure.
Last edited by Micho; 08-03-2013 at 11:00 PM.