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Hi, I've had a couple of Cory sterbai for a few months now (1" size) they've done fine. On three occassions I've tried to add 1-2 more of the same size. They do well for 4-7 days, schooling, feeding, etc and then they die.

Two died overnight. The first two are still fine!

I'm perplexed, and frustrated. I'd like to have enough for a small school.

35 gallon flat back hex. Live plants. Small/medium substrate, a mix of plain gravel and some substrate that is supposed to be plant friendly (I forget the name), eheim canister filter, lots of live plants and bog/drift wood.

Other fish are 3 leopard danios, 3 blue danios, 2 platies, 1 clown pleco, 6 cardinal tetras.

I'm completely perplexed. The only thing I can't think of is that because I turn the airstone off at night (its loud, and I thought the plants would give off enough 02 at night) that perhaps a low O2 layer forms close to the bottom because of decaying plants pieces... but I don't know. I change 5-10 gallons of the water every week with reverse osmosis water.

Any insight would be greatly appreciated.

If you read the third post from the top in this forum (titled "Read this first if you're posting about fish health", you'll see a list of "things you should tell us". Please use that "form" to fill us in on what your tank is like and the situation of your fish's "ill health".

Also, could you fill in your country (and state, etc if you live in a big country like the USA) in the profile up at the right corner of this page. That will help us give you better advice that works in your part of the world.

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Mats

Thanks, my post has almost all that information, just not in the list form. Tank set up for 5 months. I live in Boston, MA.

All those very particular test readings I don't have. I've never needed them in 20 years, atleast not so far.

oh, and temp 78-80 degrees F

jimoo wrote:All those very particular test readings I don't have. I've never needed them in 20 years, atleast not so far.

Test readings are possibly one of the most important things in that list - yes, the time the tank has been set up and temperature is also useful. But the test readings will tell us if there's a problem with the filtration system or some such.

If you haven't got a test-kit, then I'd suggest you take a sample of tank-water to the shop and have it tested for (in order of importance): Ammonia (NH3/NH4), Nitrite(NO2), Nitrate(NO3) and pH. You want to have the values of each reading, not just a "good", "OK" or "bad", as each of the measurements will be telling us something about the state of the tank.

My gut feeling is that your nitrate is high, and this is causing the new fish to go into shock and die, whilst the fish that have been living in your tank for some time are "ok" with the nitrate level. But it could be ammonia or nitrite as well.

Or it could simply be that the fish are new into the shop and sick from the transport. Have you been back to the shop to see if the remaining fish in the same tank are OK?

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Mats

The sterbai at the shop have been there several weeks and appear to be doing well.

I'll run the other tests, but in 20 years I've never had a problem with nitrate/nitrite/ammonia while I've had live plants. Most of the common community fish seem rather tolerant of going through the ammonia cycle assuming I don't just load up a new tank, which I haven't done.

Although, you may well be correct. I better run the tests.

The problem with diagnozing other peoples fish problems, is that you don't QUITE know what's going on, so it ends up being a "twenty questions" sometimes. Ruling out Nitrate/Nitrite/Ammonia is a good start - as even if it's not YOUR problem, it's a quite common problem... And according to normal triage, ruling out the common causes is the first step of diagnosing anything.

In my own personal experience with various corys is that they are relatively hardy. I have in my tank at the moment, and it's not been any problem with them.

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Mats

You're correct, of course. The most perplexing part is the two original ones are fine, the ones added since have been fine for 4-7 days, then poof!

So, an issue the original inhabitants could have acclimated to over several months, while the new fish find a shock, makes some logical sense.

The problem your having is quite common actually. Most importers receive their fish and then send them on their way, in most cases with one or two stops along the way all over a very short period of time. Usually, once they are in your LFS in may be the second or third stop all within a 7-10 day time period and then again off to your tank.

Many of them will do fine short term but have quite a hard time adjusting to "tank" life including water parameters and not to mention the unseen parasites and bacteria that may be looming in and amongst them.

If your going to bring in new fish like this that aren't quarantined at the time of import I highly suggest you set yourself up a quarantine tank with slightly elevated temps (80 or so) and use something such as PraziPro to "clean and fatten" them up a bit before introducing them to your permananet tank(s).

I wondered about that as they were wild caught corys. I've had isolation/quaruntee tanks in the past for such a purpose, but unfortunately no space for one, not even a 5 gallon. Bummer.

Aren't C. sterbai nowadays commonly available as tank-bred? If so, they should be reasonaly parasite free - at least of the wild varieties, right?

I'm definitely not saying that a quarantine tank is a bad idea, but I'm sort of thinking that's not really the problem with these fish.

I do, however, have a problem with "medicating just in case" - unless it's fairly sure that it'll do some good.

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Mats

You're all more knowledgable about the availability of tank bred Corys than I am, but the store here in MA specifically did label these as "wild caught" C. sterbai.

http://www.planetcatfish.com/shanesworl ... cle_id=313

I just read this on dissolved 02. I think this might be it. I got the 02 cycle of the plants completely wrong. The sluggishness and the laboring of the other fish when I turn the light on, the corys sitting on Anubias leaves above the substrate. Hmmn. Might be it.

jimoo wrote:You're all more knowledgable about the availability of tank bred Corys than I am, but the store here in MA specifically did label these as "wild caught" C. sterbai.

Then I have no reason to say they are not - indeed, I should have added the fact that "Wild caught" are generally advertised as such, whilst tank-bred are generally just labeled whatever species the shop/wholesaler/importer thinks they are. This is for the reason that generally, wild-caught are considered more valuable and therefore it's an "added feature" to advertise this to motivate the higher price, whilst mostly tank-bred fish are generally less expensive and thus no reason for the shop to declare them as such [of course, RELALY GOOD shops will tell you which of the two they are, rather than having you guess based on what's NOT stated].

I'm not saying I know more than you, by the way - there's no telling who knows what on internet forums...

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Mats

MatsP wrote:Aren't C. sterbai nowadays commonly available as tank-bred? If so, they should be reasonaly parasite free - at least of the wild varieties, right?

I'm definitely not saying that a quarantine tank is a bad idea, but I'm sort of thinking that's not really the problem with these fish.

I do, however, have a problem with "medicating just in case" - unless it's fairly sure that it'll do some good.

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Mats

While there are many C. sterbai available here in the US that are bred in Florida fish farms they by no means are "parasite free" !

IMHO, this is most definitely the issue as I hear it probably 25 x a day from people having the same problem !

As for "medicating just in case", when you import any fish from the polluted waters of SA and/or the inadequate holding facilities of the exporters it's not only a good idea to "medicate just in case" it would be irresponsible to not do so for not only the end buyer but also for the fishes sake.

Being largest importer of Corydoradinae in NA it would be nice to one day not have to take these steps but until that day comes it is still most necessary to do so if you wish to insure the longevity of the fish.

Thanks for the great advice and dialogue. Now I know where to get Cory sterbai if I want to try again once I fix some issues.

I had the CO2/O2 cycle with plants totally backwards. I was turning on the air during the day and off at nights. So they had super oxygenated water during the day, then at night the plants were using 02 and the air was off. I think there was a DO issue at play from how they acted before dying. The aquarium is densely planted and although I do water changes, there is an abundance of plant bits decaying (I like the natural look) but this could create an anaerobic zone along the bottom.

corysrus wrote:Being largest importer of Corydoradinae in NA it would be nice to one day not have to take these steps but until that day comes it is still most necessary to do so if you wish to insure the longevity of the fish.

But I take it _YOU_ do medicate, which means that any customer (shop or individual) should not need to repeat this, right?

I agree that fish may carry parasites (particularly wild ones).

To Jimoo - I don't think corys would be the first fish to suffocate in a low-oxygen environment - they are perfectly able to use atmospheric air as oxygen-supply.

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Mats

MatsP wrote:

corysrus wrote:Being largest importer of Corydoradinae in NA it would be nice to one day not have to take these steps but until that day comes it is still most necessary to do so if you wish to insure the longevity of the fish.

But I take it _YOU_ do medicate, which means that any customer (shop or individual) should not need to repeat this, right?

I agree that fish may carry parasites (particularly wild ones).

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Mats

Absolutely correct ! We quarantine all fish for 60-90 days before they are released for sale. This way we can medicate them as well as fatten them up so when either the shop or individual receives them they are robust and healthy which helps insure that issues such as Jimoo is having don't arise.

Ok, I think I'm just going to chill a little while, let the tank age and cycle more, keep doing water changes before trying to add more C. sterbai. I really like them. I'm generally not a Cory fan, but this species has me hooked.

You may have picked up on this already, but bear in mind that plants only produce oxygen when light is present. At night, they will consume oxygen. Therefore, it is possible that you would have depleted oxygen levels in a densely planted tank in the early morning before the lights come on and the plants can start producing oxygen again.

However, as mentioned, other fish probably would be gasping for air at the surface before the corys start suffering, and this wouldn't explain why your original corys seem to be doing ok.

If it were me, I would find a quieter aerator and avoid turning the thing off at night, whether or not this is causing your cory problem.

Yeah, I'm keeping the aeration on now. I hope it helps.

I've also been told that my using RO water for water changes might be a problem. There might not be enough calicium in the water to buffer the Ph, and perhaps the Ph is crashing over night.

So, I'm going to incorporate some tap water (after aging) to in the water change regime.

The symptom of new fish dieing after 5-7 days while the original fish are fine also fits with the fact that the original fish have become accustomed to the pure RO water while new fish just can't make that sudden transition to pure water, but it takes a few days before they die.

Steve

Thanks, I've never had a problem using pure RO water before, but you're not the first person to mention this as being a possible issue, some I'm going to mix in some tap.

An update:

Since I started to include 30% aged tap water as a part of the 1/3rd water change every week I've had no further losses and all the fish appear healthy an happy. It looks like it may have well been the PH issue.

Thanks!