Unknown problem with Blue Glolite Tetra

[Scottishscales]

I have a glolite tetra that I've had for quite a while in a tank with other tetras, guppies, and albino corys. I recently added some harlequins but this happened before I added them. I bought a purple glolite at the same time I bought the blue one but that one and all my other tetras are fine.

I have a eheim 2211 that I've been using since I started this tank and have been able to keep the ammonia and nitrites low. Nitrates have been a problem but I haven't seen any adverse affects in any other fish.

The problem with this fish is that one pupil is pinned and the other is open like normal.

The fish still eats and swims fine, no stressful breathing, gills and fins are fine, but it sometimes swims a little crooked but I think that's from the lack of sight in that eye. Any ideas on what the hell happened?

I'll try to post a picture in the comments, still haven't got the picture uploading thing yet.

Thanks in advance!

"There's always a bigger fish." - Qui-Gon Ginn

 

[Scottishscales]

Pictures. The picture on the top is the bad eye. It's a little blurry but you can see the pupil is not open. The bottom is the other eye on the same fish. Looks normal and open.

"There's always a bigger fish." - Qui-Gon Ginn

 

[Delapool]

Most curious - how long has it been like that?

 

[Scottishscales]

Not really sure. I know it was before the rasboras that I put in about a month or more ago but I don't know how long before that.

"There's always a bigger fish." - Qui-Gon Ginn

 

[Delapool]

Old injury perhaps? Is it blind on that side?

 

[Scottishscales]

Not sure if it's blind. It tends to not put that side toward the glass. But I'm guessing by looking through a hole that small and having no control over that pupil, it's probably blind.

When I bought it there were two healthy eyes so it must have happened after the fact. I just don't know when. I don't see any outward signs of a fight such as open cuts or marks where there were old ones. I would have noticed cuts. I check the tank everyday and I don't see any damage to the fins now or remember any damage.

"There's always a bigger fish." - Qui-Gon Ginn

 

[Delapool]

I don't think I've seen anything like that. Perhaps someone will know. Hopefully since a month has gone past the fish is ok.