Sick Corys / medicine & filter bacteria

Question
Hi Karen!

It's hot again here today in Autumn Australia -- what's this weather
doing?

I have three corys that had indeterminate skin problems.  It
wasn't cottony fungus and it wasn't Ich spots.  It was a sort of a
cloudiness to their skin colour that had a white aspect to it.

Anyhow, I took them out to treat in a proper hospital tank (it's a
ten gallon I had under the house and had totally forgotten about
- doh!), heater, thermometer, bubble stone and a hidey
hole....and they got SICKER.  

Oh dear.  

The white cloudiness to their skin got worse and they were so
depressed looking they were surely going to die. They would not
eat at all and just moped around hardly moving.

So I put them back in the community tank and they looked much
happier and two of them started rooting around for food again
after a few hours.

I had treated them in the hospital tank with a half dose of Fungonex
and that looked like it was killing them so I changed the water (using
water from the community tank) and tried a half dose of a tri-sulpher
tablet.  Also made them seem sicker.

I have treated the whole community tank with Fungonex -- they seem
happy enough after that and also Melafix. One of them really was
knocking on death's door last night (rapid breathing and
clamped fins sitting on top of a plant. And today it had a little
feed but still looks very sick.

The fungus now looks like slime that has gone wrong.  It is
whitish and there are a few holes knocked in it. Maybe that is the
meds breaking it up?

Will the Fungonex wipe out my beneficial bacteria?

Do you have any experience of fish just dying from depression
when it is removed from home?  Sound a bit too much to credit a
fish with...but the change in them when returned to the
community tank was quite remarkable.

I feel bad that whatever I did made them worse!  I might have
killed them with kindness.

Any ideas would be helpful -- especially if you think we are
about to experience an ammonia spike!

Warm regards,
Gillian  : )

PS In answer to your previous question about Australia (I do not
know if you get to read all the comments in the thank-you box
where I answered first up), we get some snow down here where I
am every few years.  Cold and fun for the kids but not for the
adults! Always tropical at the top of Australia though which is
muggy and sweaty most of the time (I have lived there too).

Plenty of nice bits to suit everyone most of the time. The beaches are
awesome.  So are the sharks but they only eat...um...tourists.

I hope you get to visit someday.  : )  

Answer
Dear Gillian, poor cories! Sounds like they've been having some serious skin problems.
*I would suspect your Corydoras might have been living in bad water quality that may have been irritating their skin--hence producing excess slime coating. A good water change and thorough gravel vacumming would have been the first step in getting them better. I wouldn't treat with medications of any sort unless you are certain of the illness and you have the proper medication and it is safe for catfish (not all are). For now I would keep them in as clean and fresh water as possible if you can. If I were you I would change half their water every day and keep melafix in the aquarium water (but no other dangerous meds--Melafix is quite safe and won't harm your biological filter) Don't use any other meds however. I highly believe they may be experiencing poor water quality and need many water changes and no more meds the very most.
~*~Sorry I am not for certain about the Fungonnex's harm to your bacteria. It doesn't seem to be sold around here!
What I do know is most medications (with the exception of melafix) all can severely harm and destroy all your bacterial colonies.

I don't understand why your fish are sick.. It's very strange. The two most important things to look after with fish is--Water and diet. If you pay attention to both of these things the most, it leads to very healthy and happy fish. Remember cories cannot tolerate salt, many medications, or high ammonia, nitrite, or nitrate levels.

When you setup a brand new aquarium, you can have bad ammonia spikes which can make fish so sick. To avoid this (if your established tank is cycled) you can take several handfuls of gravel into your newly setup 10gal. Or take some of the dirty filter media from the established aquarium into the new. Be on the lookout for ammonia spikes even with these "seeding" steps taken.

~Although I am not certain how Fungonex works with your bacteria. I would suspect it would destroy the colonies. Try to do a water change to get Fungonex out of your aquarium and filter your water through chemical media by the use of absorbing activated carbon which will further help absorb the medications perhaps until they do any extra harm to your biological filter.

Dying from Depression? I'm not sure with a creature like fish. I do believe they can feel depressed at times--and we all know they feel fear, excitement, and joy and of course--Stress! I know how cichlids like Oscars can beocome when moved from their current aquarium into a new enviroment. You'd think these fish--being a foot long or so, would accept the new enviroment with gusto and feel unthreatened, but I have found these fish to be the worse at feeling unsure about their surroundings when placed in a new aquarium or their enviroment is changed. On the otherhand, in the past when I've had to move small tetras, guppies, Danios and others- they happily acclimated to their new aquarium. And even ate the first few minutes after being switched to the new place. Is this because of the tiny fishes having such small brains they do not "pay attention" to their new surroundings or are mindless beings? No.. They certainly are aware of their surroundings, I do find each one to have a mind of their own. But in my case, It may be because the majority of the time, these smaller fish were moved together in large schools where they all felt safer and better about everything. While big Oscars take a while to get accostumed but are usually moved by themselves--without other Oscar company. He may feel alone and unsure about what's around the corner in his new enviroment, so this may be my case and many other cases of oscars getting "depressed" about being moved.
*I have found a majority of stressed and depressed fish have resulting from being removed from their main fish group and familair surroundings. Cories will become depressed and could even die from the stress of being alone. I have found many fish need others either of their own kind or even  another species, you get out of depressed mode and begin eating, swimming about freely, ect...
It is possible for fish to die from depression--if they are depressed enough for the symptoms of their depression is what actually kills them--not wanting to eat, lack of swimming exercise, and overall loneliness.

It is always important to keep schooling fish in groups or else they will get depressed and ill.
I hope this helps!

Well, I'm sorry to hear about your cories. Let me know if you have anymore questions or concerns--and on their recovery of you don't mind.

Best wishes,
Karen~
Ps: Yeah we get snow about once every so many years. It's great to have it, it just makes the whole place look magical. It never snows tremendous like several feet--at the most it's just enough to cover the ground. It's warm now and we get mostly warm weather all the time here. Lots of rain and thunderstorms for the past couple of days but today it is breezy and sunny.
Summers in Texas are VERY HOT. at least 98+ commonly 100F.
That's pretty neat you have sharks. I know this is a silly question--but is the Kangaroo to Australia like the Deer is to USA? Thanks for your time on me!
I love Australia, wish I could visit someday. ;-)