Danio Lost a Fin

Question

I was shocked this evening to discover that my long finned golden danio had the upper part of its tail fin completely missing (it was like a 1/2" long part of him). All that is left is small stub where that upper part of his tail fin is, and I do not see any odd discolorations or growths there. I do not have any fish exhibiting aggressive behavior (that i know of), and none that would have been able to take such a big piece of his fin off, so I am perplexed.

I have a bushy nosed and common pleco about 4" long each. Do you think they'd be munching off his fin? Or perhaps my little squirrelly Chinese algae eater (3") could be the culprit? He does always act as if he's been up to no good, and although I haven't observed it myself, I've been told that my algae eater (named Shnood) hates the golden danio and chases him from time to time.

I am considering that it may be a fungal illness, but I have been treating my tank with Wardley's Ich Out Sensitive for a week and it is supposed to help with fungus too, so I would be surprised to get something like that in my tank.

I have also noticed a tear in the side flipper of my common pleco, but I don't know if it is at all related.

Temp: 78
Ph: 8.5
Ammonia/nitrates: normal level
Size: 35 gallon with 7 small fish inhabitants


What do you think the possibilities are of why my danio lost the upper part of its tail fin?

Answer
Anna,
I would guess that the culprit is the Chinese algae eater.
They are sneaky and aggressive as they get up to size.
A better choice for this tank would be Otocinclus cats or Flying Foxes.
I would not worry much of fungus as it is easy to treat if it shows up.
However since it has not by now I would tend to think it is an non issue.
What happens is at nite when the fish settle to the bottom of the tank, the Chinese fellow sneaks up and rasps them.
There are certain fish that dine on scales of other fish exclusively.
Isolate him if you can and see if the trouble dissappears.
If you need more assistance, just ask.