Regarding the missing chunk from tail, I noticed a couple of nicks (not so big) in the other one too. I took them both out and gave them some fin repair med in the quantine tank. The one pictured above has almost grown the missing chunk back in a week ! The other one with the two smaller tail fin nicks has not repaired but not shown any signs of further damage or deterioration either. They were returned to the main tank this weekend and have been very actively scrubbing the glass and plants, no further damage sustained. I wonder if my cheeky tiger barbs were a bit too curious when they were first added.