common

Question
QUESTION: I have some common creek minnows in my freshwater tank.  I've had them for a few years without any problems.  Within the past two weeks one of them has developed a problem with her eye (I know it's a female).  At first I thought it was pop-eye so I've been doing regular water changes.  It hasn't helped.  Only one eye is affected and none of the other fish in the tank are having any problems (even the newborn fry).  She doesn't seem to be in distress.  She's eating and swimming around.  The other fish are picking on her a little though.  Not much, but a little.  The problem is...I don't know what to do with her/for her.  Do you have any idea what's wrong with her?  Should I euthanize her?  And if so, how should I do it?
ANSWER: Hi Shannon
Well I'm not all that familiar with those kinds of fish, not even sure what kind you have.  The one thing though with wild caught fish, they're going to be more prone to different parasites and such that most aquarists don't see, because their fish are tank bred.  But my first question would be, you thought it was popeye.  
Was the eye bulging out or cloudy?  
And what's her symptoms now?
How often were you doing water changes before the problem started?
Do you know what your water parameters are-ammonia, nitrite, and nitrate?
When's the last time you've added any new fish?

If it is popeye, that's usually brought on by poor water conditions.  Or, it could be a bacterial or parasite infection.  Usually doing a few water changes helps though.  May be best to try something else since you've done that.  Do you have another tank you can move her to?  Usually fish will sense there's something wrong with one, and will start picking on the sickly ones.  That stresses the poor guys even more, and usually it's downhill from there.  

I wouldn't think about euthanizing just yet.  You can try to treat still.  Let me know on those answers above, and we'll take it from there.  But here's a link, you'll need to copy/paste, on more humane ways to euthanize:

 http://www.petalia.com.au/templates/StoryTemplate_Process.cfm?Story_No=1885#ct-4

http://www.wisegeek.com/what-is-the-most-humane-way-to-euthanize-a-fish.htm

Christy

---------- FOLLOW-UP ----------

QUESTION: When I say "creek minnow", I mean the little 1-2 inch long fish that are in Northern California streams, creeks and rivers.  

Even though she's a wild-caught fish, I've had them for years and this is the first sign of any problem.  I would think, if it's a parasite or disease she caught in the wild, it would have shown signs before now.  

Actually, I think she may have been born after the initial harvest.  So, even though she's still technically wild, she was born here at my house.

Anyway, it started with just a bulging eye, hense why I thought it was pop-eye.  But it's turned into something so much worse.  It looks like it should be painful.  It could be a tumor or something along those lines.  I've looked online for other eye maladies but haven't been able to find anything remotely like this.  

The eye itself has been pushed out by something inside.  And, whatever it is, it's continuing to grow.  There's no cloudiness to the eye.  

The water is fine now.  I don't even think there was a problem with the water to begin with.  But since I thought it was pop-eye...well, I looked in a book and it said to try changing the water so that's whay I did.  

I'll try moving her to a hospital tank but I don't want to just leave it at that.  What would the signs be of her suffering?  And how long should I give her in the hospital tank before moving her back in the community tank?

Answer
I asked about any new additions to the tank because sometimes they can bring in bacteria or parasites.  This could also include any plants or rocks.  You say your water parameters are good, which is good as well.  Popeye is more of a symptom then a disease.  It's hard to diagnose fish, especially like in your situation when there's been no changes to the tank.  Realistically, people aren't going to take their fish to a vet for diagnosis/treatment, which would probably give the best result as to what a problem may be.

It very well could be a tumor growing, which there's really no treatment for.  It could be air bubbles behind the eye causing it, similar to what scuba divers get.  If you can see into the eye clearly, look for little bubbles in there.  It could be an underlying bacterial infection, like septicema.  Usually that would show red streaks on the fins or body.  Have any fish died recently?  Fish are known to be cannibalistic.  It could be fish tuberculosis as well, but usually you'll see other signs with that like lethargy, not eating, wasting symptoms.  

As far as if she appears to be suffering, that's hard to say.  I personally like to try my best to treat a fish before euthanizing.  Others believe in euthanizing at the first sign of an illness.  Everyone has a different opinion on that.  You said she's eating and swimming around fine.  I'd leave her in the hospital tank until she's well.  If she does happen to die, and you don't catch it in time, other fish may start eating her remains.  If it is a bacterial infection, that may spread it to the other fish.  If you do decide to continue trying to treat her, I'd try using an antibacterial/antibiotic food.  Most pet stores are selling these now.  I prefer the food to a regular antibiotic in the tank, because it gets the meds inside them.  If you can't find the food, Maracyn Plus or Maracyn Two are good gram negative, broad spectrum antibiotics.  

Hope that helps, and good luck with whatever you decide to do.

Christy