sick corydora

Question
QUESTION: Hi, I am very new with this whole fish thing.  I have a very sick corydora fish.  It started off completely grey with some white underneath and over the past 4 days it has turned almost white, like translucent almost.  It has a reddish/pink tone to a lot of it's body and it is barely moving around on the bottom (it used to be fairly lively); it won't even swim away if one of the other fish touches it.  Also, it's top fin looks like its shredded or something has been biting it.  We have a red belly pacu in the tank too, so maybe he's a fin biter?  I've moved the sick cory to a separate tank, although it doesn't have a heater/filter/bubbler like the original tank has, so I don't know if moving it was a good idea or a bad one.

I used to have a 2nd corydora, and one day went to feed them and he was gone.  Just completely gone. I checked all around the tank, in the tank and on the ground/table around the tank. I took everything out of the tank and completely cleaned it.  I have no idea what happened to him to this day (this was about 1 month ago).  Maybe this is related to the illness of my 2nd cory??

In the tank is the rbp, the corydora, 3 small orange fish (about 1/2 inch long with black stripes, I don't know what they are exactly), a blue gourami, and a really thin, fast, 2" fish.  The tank is 10 gallons.   I don't know the water parameter readings. The tank is heated to 78 degrees.  I change 2 gallons of the water every 3 days. I've had the tank running for 3 months.

Please help me! I don't know whats wrong with my little guy but I really like him so any advice you can give me would be greatly appreciated!
Thank you for your time!

ANSWER: Hi Caroline
It could be something was biting it's fin, or it could be fin rot.  Without knowing how big the pacu is, but I would say your tank sounds overstocked.  Those guys need over a 100 gallon tanks, they grow huge....The orange fish, you should find out what those are, they could be the ones nipping the fins if that's the case.  I would go ahead and treat the cory cat with an antibiotic like Maracyn Two.  I would also pick up a test kit that tests ammonia, nitrite, and nitrates and see what those levels are.  Fin rot is usually brought on by poor water quality.  Keep him separated as well.

I would give some thought to either upgrading to at least a 55 gallon for now, or returning the pacu.  I would try to figure out what those other fish are to make sure they're compatible for your tank.  Here's a few links with fish profiles to go through:

http://www.liveaquaria.com/product/categ.cfm?pcatid=830

http://www.fishprofiles.com/profiles/default.aspx?pnl=fresh

The orange with black stripes could be anything, initially I thought of an African cichlid, but it could be a clown loach...just lots of possibilities.  

For the fish disappearing, that happens.  Happened to me few months ago, I had 2 of my older cory cats just go missing in action on me, never found any remains of them.  When a fish dies, the other fish will eat at them, and if not caught, just the bones are there, which can mix in with the substrate.  It's even possible for them to find the tiniest hole and jump out, and if you have dogs or cats in the house they'll eat them.  It's not uncommon to not find any remains.  

Hope that helps and let me know if you have more questions.

Christy

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

QUESTION: Ok, so I did a lil research and figured out that the orange w/black striped fish are tiger barbs.  Should I move the barbs to a different tank? Are they the ones biting the one fish's fin?  I'm going to get a water testing kit soon, so I'll be able to know if it's fin rot or something nipping, although I'm really thinking it's a nipper, and maybe it isn't the pacu?  The sick cory is looking better, his color has returned to normal, although he hids under this ship thing for 99% of the day.  Thanks again!

Answer
Ahhh tiger barbs....known fin nippers :)  My guess would be it's them that's injured the cory cat.  It's recommended to keep them in a large group, like 5-8 because it supposedly helps them to keep their fighting amongst themselves and they won't harrass the other fish.  I wouldn't recommend putting that many in your tank though, because of it's size.  If you have another tank, I'd move them to it.  

Once you get your tank straightened out, cory cats also prefer to be in groups of at least 3-5 minimum.  With your tank, I'd say you could safely add 3, but the pacu is still going to be an issue for you because of his potential size.  And actually, I'm not for certain, but I believe the pacus love to be in groups as well....but you'd need a ridiculously huge tank for that.

For the cory, that's good he's looking better.  You could pick up some MelaFix-it's a natural remedy that works fairly well with injuries to fins and tails like yours has.  

Christy