Rapid Death Of Corys

[Funktion]

Hi there,

I'm new to the forum, but come here off the back off a Google search seeking the knowledge of others. As a relative newcomer to the aquatic hobby (I've only been keeping tropicals for about a year or so) I usually speak to a work colleague who has a great deal of experience in this field, but he's on his honeymoon and disaster seems to be striking my fish!

I set up a new tank about a month ago - a Juwel Rekord 120 to be precise. I had it cycling using the water from the smaller tank I upgraded from (approx 60L, so half of the water in the new setup was mature), planted it up, and started to introduce fish after a couple of weeks. First I moved a few glo-lite tetras and black neon tetras up from my downstairs tank. No problems there. A pair of swordtails were then moved up from downstairs and have since given birth to four little-uns, so I guess they're pretty happy with the water too. Then a pair of Kribs were introduced - other than a lover's quarrel they're still alive and well.

During this time (just over two weeks - each batch introduced on the Saturday of each weekend) I also introduced a few Corys. A single albino cory was moved in with the tetras at first. He was nearly a year old and doing quite well for himself. I bought him an apprentice - another albino - a week later. Then finally (with the Kribs) I introduced two more albino Corys and two bronze Corys.

3 of my Corys are now dead. First, the single young albino. I figured that even though I bought it from my usual source (an excellent local pet shop) it was just a dodgy fish so got rid of the corpse without examining it. Then I came home a couple of days later to find the more mature albino floating on the surface. This concerned me as he has never shown any previous signs of ill health. Then I come back from work today to find another albino in its death-throes and one looks pretty likely to follow. The symptom in all of these cases is bright pink/red gills, occasionally spreading to the side of the head and body (possibly due to scraping - scale loss/gill damage?). In the case of the more mature Cory, most of his body seemed to be almost 'sunburned' when I found him. From a veterinary pathologist's point of view (my trade - non aquatic animals, unfortunately), this looks to me to be some sort of bacterial infection. Does anybody have any ideas? The gills of one of the bronze Corys is also looking slightly reddened - hopefully he's not looking at coming down with the same. I'll call the pet shop tomorrow to see if they've had any of the same batch of fish come down with anything similar - if not, then I gues I'll have to look closer to home.

The temperature of the tank is approx 28c (thermostat will go no lower), all normal tests (pH, nitrate/nitrite, etc) are within perfectly acceptable ranges, the tank is well aerated and filtrated, the plants are thriving, and all the other fish seem to be doing just fine. I love Corys to bits, and was looking at getting about a dozen of the little critters, but I don't want to introduce any more until I know why I'm losing them.

Sorry for the rambling post, but I wasn't sure what sort of detail you guys would need from me. I hope somebody can help/advise me.

Cheers.

 

[stang1]

What are the exact readings of your Nitrite, nitrate and ammonia? This may give everyone a better idea of what the problem could be.

 

[Funktion]

Good point. Last night, when tested before a partial (approx 1/4) water change, the results were:

Ammonia - 0.25 mg/L
Nitrite - 0.00 mg/L
Nitrate - 15 mg/L

 

[Funktion]

He's giving it up. It looks like the sick one is on his way out. Attached is a picture - along with the red gills that can be seen goes rapid respiration and a general lack of movement interspersed with occasional bouts of frenzied activity. I don't think he'll last until morning. My final albino is looking less active than usual (missing his friends?) but other than that I'm hoping that the three remaining Corys will pull through.

 

[stang1]

It sounds like some sort of bacterial infection and could have been caused by the ammonia in the water.
I would perform a 30% water change to try and bring the ammonia down as it should read 0. However, the ammonia doesn't seem dangerously high, so may not be the main cause and I'm not sure how sensitive Cories are.

 

[Funktion]

Yeah I figured the ammonia level may be due to me introducing the pair of Kribs and four Corys on one day. As I say, the test was carried out before my last water change (approximately 48 hours after those six were added), so hopefully it was just a small increase and will get converted away pretty sharpish by the filter. I'm not overfeeding, and the plants are thriving so there should be a minimal amount of decaying organic matter in the tank. Here's hoping...

Cheers for the swift responses.

 

[stang1]

I really hope that you can sort it out and I wish I could help out more. I tried looking on Google and the inflamed gills seems to be due to water quality. A water change will help with this but I don't know if your Cory will make it.
If he does, then it might be worth popping to your lfs and seeing if there's something you can treat him with.
Good luck and let us know how you get on.

 

[-germ-]

As mentioned the water conditions need to be perfect with ill health in the tank, maybe look into gill rot/branchiomycosis a fungal infection known to result in reddening of the gills. Its fairly uncommon but don't suppose (as a lot of the 'literature' on the net suggests) that the gills would actually have to rot away to suggest gill rot, reddening of the gills is the most common symptom in fish suffering this, with physical rot being comparitively rare.
If it is water condition related (i have this with a 'rescued' gourami) their may be a secondary illness resulting from the poor conditions/stress.
Maybe look into treatments containing phenoxyethanol which is feted as having mild fungicidal properties as well as being a bactericide.
Good luck to the remaining fish
Let us know what happens.....

 

[rowdyburns21]

Sorry to hear about your losses Ive found that albino corys are extra sensitive to water conditions where as the peppered corys seem to be a bit hardier! Also corys like temps under 25c ive found mine go real quite if the temp gets above that. It sounds like everytime your putting new fish in it is starting a mini cycle therefore the albinos would be feeling this due to their sensitive nature, as you still have ammonia i would suggest a 15-20% water change per day, and because no nitrites are present that would have me believe theres still a mini cycle going on, I know you transferred the water from your established tank but see if you can also get a bit of established filter media to throw in as well!! hope this helps.

 

[Creature Seeker]

It looks like you've added too many fish too quickly. The water you used from your old tank won't have any bacteria in it. So while you left your new tank running for a few weeks it wasn't cyling as no ammonia was present to feed and grow any potential bacteria unless you had added mature filter media from you old tank (e.g. gavel, sponges...). When you added your first lot of fish, that's when it started cycling. I'm guessing that the ammonia was a lot higher at first, but as your tank started cycling, ammonia levels have started to decline. Unfortunately your cory's may not have been able to handle the prolonged exposute to the ammonia levels. I may be wrong but I think ammonia burn fish around the gills, which can cause trouble breathing. This would explain their red gills.

...

 

[Funktion]

Evening all,

Just got in from a long day at work and - good news! - the previously pictured cory is still with me! He's currently sulking in a cave, so I can't actually get a good look at him, but he's still breathing.

Thanks for the posts in my absence today. With regards to the maturity of the filtration system, the Juwel box filter was restarted after a 2-3 week rest, so the bacteria in that may well have been long gone, but I have also got a Fluval 3+ in there to give out plenty of bubbles and keep up a decent level of filtration, and the pads in that are taken from a well-established tank.

Regarding the heater - would anybody recommend that I look at getting a different one? As I say, the thermostat won't go any lower than it is, and it's at a steady 27-29c. My other tank has always fluctuated between 25-27c, and I must say that I personally feel more comfortable with that temperature. I know that the LCD thermometer on the tank is indicating the correct temperature as I have checked it against a mercury thermometer.

I'll put on a brew now and do some more water tests while I wait. Unfortunately, it's going to be tomorrow night before I can perform another 1/4 change as I've had a stupidly long day and it's time for bed after my brew.

I'll get back to you once the tests are done.

 

[stang1]

I'm glad your Cory is still with you. The temperature shouldn't be too much of a problem, most of our tanks are kept at about 27C. It might be worth buying one just in case of emergencies or piece of mind. I've got 4 spare heaters sat in my cupboard just in case but then I am paranoid about something going wrong.
Keep us posted on water stats and do a water change in the morning if need be.

 

[Funktion]

Tests have come back looking good. Ammonia levels seem to be undetectable now, and the Nitrate is still looking:

Ammonia - 0.00 mg/L
Nitrite - 0.00 mg/L
Nitrate - 15 mg/L

I'll keep my eye on eBay for a cheap backup heater (or two). And I'll get another change done as soon as possible.

Thanks for all your help - I'll keep posting on this forum now that I've found it, and start this thread up again if the fish show no signs of improvement and it seems like an infection rather than a water quality issue.

 

[stang1]

Those readings are a lot better!
How is your Cory doing, any signs of improvement?

 

[rowdyburns21]

Id still be inclined to say its too hot for the cory!! just my personal experience