Problem stocking new Cory group - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 09-13-2012, 09:55 AM Thread Starter
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Problem stocking new Cory group

Hi all, I am having an issue stocking my initial group of Sterbai Corys for my new tank. This is a 29 gallon, fully cycled, planted tank with gravel and two pieces of driftwood. I've been testing every day with a master kit (to make sure I'm not overstocking too quickly and such). Ammonia 0, Nitrite 0, Nitrate at 10-20 (up to 40 before a 30% water change). pH is 7.5, very soft water (I forget the numbers from the utility but if I remember correctly it was about 2 on the hardness scale).

I initially planned to start with my school of Lemon Tetra but the lfs was out of them so I decided to start with the Corys. I purchased 3 to begin, spent the hour acclimating them by temp, then 15 minute intervals of adding my own tank's water to their container. Added the fish and they have done very well, exploring, zipping around, parking under the wood. I monitored the water levels and after 6 days of no change (except nitrates) I did a 30 % water change and got 3 more Corys to complete the set. Did the same method of acclimation and one died within an hour, the other two within 8 hours. Original 3 (I assume) still acting fine.

I thought perhaps the stress of the trip and new tank had been too much, took them back and got 3 more. Two of them died within 2 hours and the 3rd seems to be acting as happy as the original 3. Total of 4 still alive and apparently happy (not acting oddly as far as I can tell from reading up on Cory behavior). Tank parameters still good this morning, no ammonia, no nitrite.

The only thing I can think is that the lfs says they keep their pH at 6.8 and mine is around 7.5 and it's too much of a change even taking time to acclimate them.

I'd love to have 6 to have a happy group, but my budget for fish is going to get pretty stretched if I have to buy multiple fish to find one that can adapt to my tank.

Any thoughts would be appreciated.
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post #2 of 4 Old 09-13-2012, 10:12 AM
How long has the tank been cycled? Cories typically need a mature tank, usually one that's been cycled for several months. But when I first set up my 29 gallon, and added my 5 initial cories only a few weeks after my cycle finished, they made it, and six months later are still doing well, especially happy with the other 4 i've added in the last couple of months.

The pH could be a big factor for sure, especially if you acclimated them a little bit faster than you realized. Change of water chemistry can really stress a fish out, and of course stress will hurt and even kill fish. It seems like captive bred fish do a bit better with a change in parameters like that, so maybe going much more slowly than you first thought when acclimating would give you a better chance with the cories.

It could have very well been the stress of the car ride. When stressed, cories (if i'm remembering correctly) produce a lot of ammonia, and when traveling with all the cories in a little bag, there'd be a lot of stress and a lot of ammonia.

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post #3 of 4 Old 09-13-2012, 11:08 AM Thread Starter
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The tank is newly cycled, I'm trying to do my initial stocking of the tank, so perhaps that's part of the stress but my levels had been so consistently good I had hoped it would be ok. To acclimate them I tried to follow the guide that I read and I had the bag in the tank for 15 minutes to acclimate the temp, then I emptied them into a container and added 1/2 cup of my tank water every 15 minutes for an hour. After that I netted them into my tank.

The car ride is about 20 minutes, then the acclimation time. Perhaps a drop of Prime in the water when first releasing them from the bag would help in case of ammonia levels?

I have read that Corys don't do well with stress but I'm not sure how to lower the stress of the move any more than I have because I'm trying to make the trip as short as possible.

I've never had Corys before so all of this is new to me (as is setting up the tank properly with plants and the cycling process) but I really like the ones that have done well and would love to get two more to make it through this process.
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post #4 of 4 Old 09-13-2012, 04:27 PM
How do they ride home? Do you put them in something dark, or do you let them ride in the front seat? I am still learning the best way to get my fish home too. Someone recommended bringing a box that can be covered, so the ride home is dark, and they don't get as stressed. I haven't bought many more fish since I got that advice, but when I did on a whim, I had them put the bags inside of a paper bag. My nearest pet store is within walking distance, so the ride was only like a minute or two, but the dark enclosed space can really help easily stressed fish.

The Prime might help! I honestly haven't bought any Prime yet myself, but i know it can help neutralize toxins like ammonia. I need to get a bottle of that!

In any case, the cories may be alright with just the first four if you can let the tank mature a couple more months. Then try the other precautions we've come up with ^-^

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