Also, now I suspect that the damage to the fins may not be due to
aggression, but because of some disease like fin rot. There is a lot
of red coloration at the base of the fins and the fins seems to be
shrinking. I am planning to use a salt bath as an anti-bacterial
remedy, as recommended by a book on fish diseases I have.

Unfortunately, the female lab died yesterday.. it looks like she had a
disease after all. Her fins were almost completely eroded and there
were red sores everywhere. My fish diseases book tells me thats a sign
of fin rot. Has anyone encountered this before? What is a good remedy
for fin rot?

Thanks,
satyen