You know, this does look like it might possibly be something externally
inflicted. I'm intrigued by this rainbow shark idea because I made a
change in the tank recently (just 4 days ago or so) having to do with
this very shark.
I recently trimmed a very large amazon sword that had been developing a
bad case of algae secondary to a new flourescent light I tried. This
shark mostly hid under this plant, kept there be a chinese algae eater
that did not like him. When I trimmed the plant the shark didn't have a
good place to hide anymore and began fighting very aggressively with the
CAE.
To try and make a long story short, I did not like the CAE anyway so I
removed him from the tank and destroyed him because he was way too
aggressive. At that time the shark reclaimed a specific rock in the
tank that the CAE had previously run him off of. In turn, the shark
began to be pretty aggressive in guarding that rock. He would chase
away any bow that came near it.
Tonight, I sat for a good hour in front of the tank and just watched the
interaction between the shark and the herbies. This shark is ramming
these fish pretty hard and after returning home from work, I notice one
of my herbies has half its tail missing, as if it had been nipped
repeatedly and another has a good portion of its 2nd dorsal gone as
well. These "injuries" appear to be unconnected to the previously
described lesions.
I never realized this rainbow shark had the potential to inflict this
sort of damage. I've had this shark since before I started keeping bows
and he is pretty big (about 6" TL) and fat. There is no other fish in
the tank that could or would nip these fins like this. Perhaps this
could explain the loss of the SAE as well.
This is my longest running tank which receives 30% new water a week. I
haven't added any new fish except the herbies and lacustris. I believe
my filter is fine as it receives regular maintenence.
Anyway, I plan to break down and redo this tank (70 gal) tomorrow. I
will move my other fish to a new 30 I have. I'll then replant and get
this tank ready for some nice convention purchased fish. I will trade
this shark for some fish food.
I really feel bad for these herbies. I've learned so much about keeping
fish in the last 2 years but I really feel stupid now. To think my
utter ignorance has possibly cost me these very beautiful fish, not to
mention I paid plenty for them.
Oh well...back to the drawing board
Thanks
Jim