I have had my neons for about a year. They alll seem helathy and look good. However of the past few weeks I have started to notice a black lin develop under the red fo
the biggest one. It is at the bottom of the tail under the red. I dont see it on any others yet just the one.
What does ti mean?
I couldnt get a pic but I found on online it looks a lot like this but maybe just a tad darker and possibly a smidge thicker: