# Hoping to get a hypothesis



## AshRD (Jun 15, 2011)

Hello all. I am new to the hobby and I recently had 2 new corydoras catfish die in my tank. I am wondering if anyone has any insight as to perhaps why.

I started a 20 gallon (tall) in its cycling about 3 months ago. After a month and a half it was processing quite a bit of ammonia fairly well. After a complete water change I got 3 (1 male and 2 female) platys and 4 albino corycats. (unsure of their sex) I monitored the water by testing over the next week and half every other day. I did a 25% water change 1 week after introduction. It was about 2 days after this that I found a cory cat upside down on the bottom of the tank. About 5 days later one other also turned up that way. In all my testing, the only rise above zero in ammonia or nitrite levels was to .25 ppm in nitrite before dropping. I've been keeping the water at 75-77 degrees F. Anyone have something that I may have overlooked.

The levels of ammonia hasnt rose above zero, nitrate had that one small rise and ive been changing out water weekly as well as vaccuming. Maybe the platy is causing stress or maybe some intrusion of my hand/vaccum caused them stress.

I am just wondering if someone can think of something I may be missing or if it just happens sometimes.

Thanks!


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## holly12 (Apr 21, 2011)

I doubt it's the gravel vacuuming or your hands being in the tank. (I've got my hands in my 10g almost every day feeding my ADF's and fixing plants that they pull up,) and the fish don't seem to care either.

I don't think a platy would bother Cory's (especially since he's got 2 females to chase), but if I'm wrong, someone correct me.

It sounds like you had them for about a week and a half before 2 of them died.... is it possible they were weak or ill? Did you notice any white spots or any fin rot or bloating or anything on the bodies?

You are sure your tank was completely finished it's cycle? (Did you do a fishless cycle with ammonia or did you cycle with hardy fish?) When complete, you should be able to does your tank with ammonia and have the ammonia at 4ppm, and then have the Ammonia and Nitrites at 0 in 24 hours. I don't think the complete water change would have done it, as there isn't really any beneficial bacteria in the water column.... it's all in the gravel and filter media, but again, if I'm wrong, someone please correct me.

Do you have a filter for the tank? Is it the correct size for the tank you have? From what I've read Cory's love highly oxygenated water, so if your filter is not cleaning the water and bringing in 02 (ex: from agitating the water's surface,) that could be the problem. An air stone would be recommended with cory's to give extra oxygenation to the water.

Are they getting a varied diet? Fish usually do better when you don't feed them one food every single day. (For example, my fish get a veggie flake in the am and a protein based flake in the pm, as well as frozen blood worms a couple times a week for a treat.) They pick at the algae wafers that I throw in for the Oto cats too.

Before putting the fish in the tank did you test the water they came in and compare it with your tank water? Sometimes a big change in water parameters will kill fish when you first bring them home.... although I would think it would have killed them sooner. Same as acclimating them. It needs to be done slowly, but again, I'd think it would have killed them sooner if that was the problem.

Sometimes fish just die. Who knows how long they were at the fish store for... maybe they were old.

I hope some of this helps and good luck with the rest of your fish. (Are you going to replace the Cory's? I read somewhere they like to be in groups.)


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## jrman83 (Jul 9, 2010)

What method did you use to cycle the tank? Just from the info you gave, doesn't sound like your tank was cycled.


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## AshRD (Jun 15, 2011)

Yes I did a fishless cycle. It took about 4 weeks for it to get established. I was dumping a teaspoon or more of pure ammonia about every week and it was being processed in a fairly short amount of time. The water oxygenation may be a culprit. There is not alot of agitation from my filter, but overall with the water changes and the fact that there are so few fish, I'm not sure. I may want to get something to add just in case.


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## jrman83 (Jul 9, 2010)

Then what method did you use to acclimate the fish before putting them into the tank?


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## majerah1 (Oct 29, 2010)

If you were cycled then either the corys were not acclimated right,or they were ill.Any signs of distress(IE,white spots,cottony growth,clamped fins,red streaks,or gold shimmer when shining a flashlight)Tell us the process of acclimation,if you dont mind?


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## Subaru4wd (May 6, 2011)

Did you monitor your PH? When You did your waterchange, did you check the PH of the water entering the tank? A ph change of more than 0.3 is enough to kill your fish. 

Also a 25% water change on a 20gal tank maybe alittle excessive. I would have done 10% with RO or at the least leave your treated, new water sit overnight to stablize before you do the water change.


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