What Is This?

[This Old Spouse]

I've been watching my 55g closely today because there seems to be a spawning frenzy going on, and I was looking at my LFBSTs and notice this black spot above the right eye of one of them:
 

 
Another photo so you can see there shouldn't be any black right there:
 

 
It's a bit out of focus but you can see the others don't have the black spot. She's acting normally but is this something I should be panicking about???

 

[This Old Spouse]

Maybe a clearer photo. You can see the fish on the lower left for comparison.
 

 

[Mikey1]

She's acting normally but is this something I should be panicking about???

 
no....quit worrying so much....
 
not all dogs have the same markings, not all kids have the same color hair....

 

[This Old Spouse]

But this wasn't there yesterday. That's what worries me. None of the others have it, and it's only on one side.

 

[TwoTankAmin]

A lot of fish exhibit different coloration when in spawning mode. I have not kept these fish so I can not say this is the cause, but it was the first thought based on your post. I suggest you look on some specialty sites which would cover the fish and see what you find in this respect. Since I am unsure, I can't tell you is insn't something else entirely. Also you might try a Google search by typing in the "latin name of the fish + spawning". Using the common name can work too.

 

[eaglesaquarium]

I was thinking that it might be a spawning coloration.  My harlys get much redder when spawning - never have had any eggs that last long though.

 

[This Old Spouse]

But wouldn't it show up on both sides of her head?

 

[TwoTankAmin]

That is why I suggested you check someplace they should know for sure. I have been lucky to see some neat stuff happen in my tanks and have learned there is regularly more that I see for the first time. So it might be those fish get the color on one side I don't know. Sometimes logic helps us figure it out, but sometimes it can be a distraction.
 
I think one good clue might be the nature of the marking. If it is just that it suddenly appeared that concerns you but it looks like a normal form of coloration as opposed to damaged or diseased tissue, I would lean towards it being a natural thing. Behavior is also a good clue. Are the males hanging around her? Are they chasing her? Are they displaying for her?
 
edited to add:
 
A quick look I found this- not sure if its right or not "During the breeding period, both sexes tend to darken their color. Black Tetras kept in a suitable environment and given nutritious food will also display darker colors than other Black Tetras."
 
edited again to add this vid of BST spawning. you can try running an dfreezing it. I though I could see a somewhat similar maring on one of the fish- but I have old eyes.

 

[eaglesaquarium]

  Not everything is bilaterally symmetric.  Just look at the Pittsburgh Steelers helmet.
 
 
Just kidding, of course.  The behavior for me is the biggest thing.  If the behavior is the same, the coloration being the only difference, I wouldn't worry too much about it.  Going to an "expert" site for serpae tetra makes sense though.
 
 
Is there any "fuzziness" or anything like that associated with the marking?

 

[TwoTankAmin]

here is an even better vid. if you stop and start it you will see a number of fish show a black marking near an eye.
 

 

[This Old Spouse]

Thanks for your efforts. I don't see anything that looks like mine. But since her behavior seems to be perfectly normal atm I won't worry about it ... yet.
 
The males will go almost black when they're feeling amorous, but not get spots like this one. A waiting game, I guess.
 
The cory are all still spawning. It's crazy town in there!

 

[eaglesaquarium]

Must be spring.

 

[TwoTankAmin]

When tanks go into spawning mode it can get nuts. Some breeders believe one can help trigger fish in another tank to add water from a tank where similar fish are spawning as it moves "spawning related hormones over" I have talked to cory and angel breeders who have done this but not to anybody trying it cross species.
 
It can sometimes be climate related things that set fish off. I have had multiple tanks all start producing fry the same week after a big storm.

 

[frapadoodle]

I may be wrong, but judging from your photos and the videos, it seems normal. But I am no expert.
It may just be a bit of understandable paranoia after the tigers.

 

[This Old Spouse]

"Understandable paranoia." I think I'll hang onto that one.