Well, all his plants are the silk ones, and he has one sort of bridge thing... but I don't think the fin was actually torn. The spot looks smaller and less white today and the tuft of fuzz on his dorsal fin is completely gone. And I could swear his fins and scales have turned a much brighter blue... ?????
I didn't treat him at all! I don't get it... but I'm certainly not complaining! Still definitely keeping a close eye on him though just in case it comes back...
And on a side note I got him Omega One and Hikari pellets today. So far he has eaten neither, but... we'll see.