Problems Adding New Corys

[tsimajad]

I have a 60-gallon tank for about 4 and a half years now. Through all my difficulties, mistakes, problems, diseases... and susequent learning over the first couple years, while many fish died... 4 Emerald Corys (Brochis splendens) survived. Now, I have kept tank conditions very good for the past couple of years, This past summer, two of them died... ...I bought two more and they joined the remaining two and lived happily and healthily until Hurricane Sandy struck and I was without power. I did my best to change water each day, adding hot water each day to keep the tank warm... and doing my best to manually aerate the water. 2 corys died (and one oto). I got the tank back in shape... added some more emerald cats, and within a week they all died. They were medium to small. I then bought a couple large ones, and within a few days, they both died. I went to a different store yesterday, bought three Sterba corys (Corydoras sterbai) two medium and one small (to try a different species) and this morning two were dead.

Tank chemistry is very good (at least those things I regularly test). Low/No ammonia... nitrates and nitrites low. pH and alkalinity good. Soft water but not too soft. I change about 25 gallons every two weeks, change the charcoal in the filters, vacuum the gravel, etc...

A few weeks ago I did a major cleaning, where everything comes out but the fish and the gravel (which I do 4 times a year) and change 30 gallons or a little more. This particular time I was having a hairly brown algae problem. All plants (artificial) and other decorations came out and I had them soak in chlorinated water to kill the algae... I then rinse them off many times to get rid of any residuals from the bleach... tested the water the plants and things were in before letting them completely air dry and then returning them to the tank. This whole process took a few days. The fish must have felt like they were back in the sparsley planted store again!

All done, water chemistry excellent.

The first few corys died before I did all this. The next two additions of corys came after all this.

One note: The emeralds are without their barbels since the summer sometime. I never could figure out how they lost them, and they have not grown back.

Other than the corys, all of the other fish are thriving! The other inhabitants include:

10 x tiger barb
4 x gold barb
10 x zebra danio
4 x bristlenose pleco
1 remaining molly (female)
7 tetras (bleeding heart, serpae, bloodfin). I want to eventually replace them with cardinals as I had a year ago until a case of ich killed 15 of them within a few days.

Any ideas? Do I need to take even extra care when adding corys? I typically empty the fishbag into a container, with the water from the bag, and slowly add water from my tank to that water to help the new fish adjust to the different chemistry. I have read some people recommend doing this more slowly with corys. I don't want to have only two in a 60 gallon tank, but I want to make sure I do this right.

Thanks in advance.

 

[snazy]

Low/No ammonia... nitrates and nitrites low

Sorry to hear about the problems you've had with the tank and corys.
The ammonia/nitrIte need to be constant 0. Any other reading indicates a problem with the tank and could be the reason for the cory deaths.
Personally, I find corys very hardy fish.
Considering that new fish you add arey dying, it could be improper acclimating and difficulty adjusting to different water condition. Read about drip acclimating and try that before adding new fish.

 

[eaglesaquarium]

It might be a case of "old tank syndrome". I question your nitrate results. The API kit is notorious for giving false lows - unless you've been shaking and shaking the 2nd bottle, you probably aren't getting proper results from that test.


Here's what I would suggest:

First, you need to ensure that your ammonia/nitrite levels remain ZERO. ALWAYS ZERO.
Second, don't use carbon in your filter unless you need to remove meds from the water column.
Third, increase your water change FREQUENCY - every two weeks is a bit too infrequent, in my book. I'd suggest every week - 25%. I'd also suggest a monthly 50% water change, and I also suggest a 75% water change every 6 months.
Fourth, a slow acclimation process is best for ALL fish, not just cories. It is more important for some species, but I've never heard that brochis sp. are particularly "sensitive". I use a drip acclimation process. http/www.liveaquaria.com/PIC/article.cfm?aid=157 You can just use airline tubing (really cheap) and tie a knot or two in the line to slow the drip to whatever you want.


If you do all these things, it should be just fine. But, until your ammonia/nitrite are a SOLID ZERO, and you have completed a bunch of water changes to keep the water fresher, I wouldn't add anything new to the tank. I understand the hardship of power loss. But, now that you have power restored, you need to correct the damage.

First thing you should do is to do 25% water changes every other day for a week. Add the water slowly to allow the fish to acclimate to the new water. At the end of the week, I'd do a 50% water change to bring the level back as close to the tap levels as possible. Then let everything sit for a month to ensure that everything is fine in the tank (doing 25% water changes each week). Then another 50% at the end of that month, and if there are no issues during that time, you should be ready to add some fish.