Get more of the same type or get another type completely


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Sep 7, 2021
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I am just musing now, not running to the store or anything. I am having hard time with my largest tank lately. I find it a tad boring, I keep watching it more, trying to find ways to improve it and spend a lot of time thinking about it.
Now I turned my attention on my corydoras. I have very much wanted corydoras almost more than any other fish when I was setting this tank up over two years ago. I was excited from all the videos, I did my reading, I had high hopes.
I feel like I am very disappointed in them though. I have a group of 13 sterbai corydoras. Some of them are over two years old, some of them are over a year. I started with 12 sterbais, after a year I bought 10 more, put them in a quarantine for a month and after putting them to the main tank, I kept losing sterbais one by one. Not sure if all the older or some of the youngers, but in a span of few weeks I lost 6 for sure. No clue why, no loss on other fish, it stopped suddenly as it started. I had a thread here too, guess some bacteria infection or parasite that the older corydoras were sensitive to. I lost three some time before/after too, maybe maintenance issue, maybe feeding issue back then, not sure. So now I have 13 and fear of adding more of them and repeating the same scenario. Last loss of my corydoras december 2022.
I even netted out the sterbais to my then empty cube to attempt to entice them into breeding few months ago, but no dice. I moved them back to the main tank after a month.

But here in lies the question. The sterbais are super not active. I mean all they do is sit, occasionaly after a water change they will swim and chase, but most often than not, just sit. They are not scared of me, I can watch them from afar and still they only sit still. They do not seem to be scared, when I feed they will happily munch on pellets from the surface where they join the bolivian rams I have, they are not bullied from the food as far as I can see they just rest. They will sit in anubias leaves perched like in a hotel, on the sand substrate, under the wood but also out in the open, not huddled under a shelter kind of behavior.

I wonder .Should I attempt again to increase their school to around 20, will it be better. Or should I buy 10 of different corydoras species, like panda. I am not expecting them to school together or anything, but I read they are more active and curious. Or should I look for a different bottom dweller. Or focus more on the movement in the middle part of the tank and leave the bottom dwellers be. I understand from some keepers this is their sterbai natural behavior, but also some other say their sterbai are very boisterous and always active. Could be overfeeding/underfeeding or feeding in general, sure
Could be me too.

Water temp is 25, ph is 7, water is soft. Tank is 360 liters
Sounds like they’re not hungry, in general. If they were hungry they would be actively looking for food. If they’re full, or if there’s no food to be had, there’s no reason for them to be active. Corys naturally dig for their food. You could try stirring some up with the top mm or two of sand so it’s very slightly buried...
Sounds like they’re not hungry, in general. If they were hungry they would be actively looking for food. If they’re full, or if there’s no food to be had, there’s no reason for them to be active. Corys naturally dig for their food. You could try stirring some up with the top mm or two of sand so it’s very slightly buried...
I do water change with sand vacuum every two week ( the other week no gravel vac) and sure, they do like that. I also sometimes feed microworms who end on the substrate, that is a joyous day :)
Sterbai are one of the more notorious corys for self poisoning during transport. When we consider how many times they may be caught and bagged between where they are born and when we acquire them, it is not unusual to have them arrive in a weakened state. There are a number of species which can do this.

Basically, they have the ability to secrete a substance which is intended to put off a predator long enough for the cory to escape. In the wild this substance dissipates fairly quickly. But in a fish bag with little water, it becomes toxic. There is a method one can use when shipping corys known to self poison. But is is far from universally used.

The method is called "kick the bucket." One places the corys to be shipped into a bucket containing clean water. One then kicks the bucket a couple of time to "scare" the corys. The purpose is to get them to release the toxin into the bucket water. After a few minutes one chnages the water and then repeats the process. To be safe when I do it, I go for three rounds.

After the final round one just removes the fish and bags them in clean water. I have done this a number of times and have never lost a sterbai in transit (so far). I have however, received them and had them been DOA or they had died not long after they arrived. In cases where they are going to die fairly soon after arriving you can usually see they are quite red where they should not be.

It is possble for sterbai to go through self poisoning to some extendt but not to die right away. But they will have suffered internal damage which leaves them weakened and more susceptible to diseases. Bear in mind that harm can have been done anywhere along the transport chain, and there may be no way to know it. The sterbai that have done the best for me were ones I took in trade for some of my plecos. The person with whom I traded was a sterbai breeder. I expected to be getting about 20 smaller sterbai. He ended up giving me a bag of 50 adults who spawned almost immediately. I had wanted the sterbai to keep a few for myself and to sell the rest. So I was not set up to receive 50 full grown sterbai and I had to overstock them for a while. The result was they ate most of the eggs and I only had a few babies actually born.

The upshot of this is, if you can find a breeder who understand this stuff, you will be more likley to acquire healthy sterbais.

Added by edit

Atter writing the above I headed over to PlanetCatfish to look for the paper on self poisoning. I found this instead and it may be of help for anyone who receives self poisoned corys. There is a way to reverse it.

Hamade, S., 2021. The Reversal of Self-Poisoning in Bronze and Albino corydoras: A Recent Study. New Visions in Biological Science Vol. 7, pp.31-36.
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We need to be careful what we believe. I very much doubt that quoted paper was peer reviewed. Written by an aquarist who calls the family Callichthyidae the Callichthys family, and states that the albino Bronze Cory is a different species to the Bronze Cory.
It’s mainly lineage 9 Corys (eg C. sterbai) that self- poison.
The author (I’m guessing) assumes the albinos were Bronze. It’s generally believed by most Cory experts that lineage 7 species (eg Bronze) do not self-poison, even though they have the (vestigial) glands. I suspect the reason the albinos didn’t “recover” as quickly was that they were C. paleatus, or even C. sterbai.

A much more humane method than shocking the fish by kicking their container, is to bag them individually for transport, which most knowledgable suppliers will do.
All my Corys come single packed. A shipper that sends a bunch in a bag doesn't know their trade. But I suspect that the better shippers still do the bucket kick before the single pack. If someone is going to kick the bucket, it's better that it be literal.

For the Corys @Beastije has, temperature could contribute, as could water flow, but it is a small tank and they may simply have nowhere to go.
All my Corys come single packed. A shipper that sends a bunch in a bag doesn't know their trade. But I suspect that the better shippers still do the bucket kick before the single pack. If someone is going to kick the bucket, it's better that it be literal.

For the Corys @Beastije has, temperature could contribute, as could water flow, but it is a small tank and they may simply have nowhere to go.
It is a 360 liters tank... They don't utilize even half of it on a good day. Today I added more stem plants to one of the open areas in case they like it better.
Btw my coeydoras didn't die after shipping and after quarantine i moved them via net one by one to the big tank. I doubt they poisoned the others but anything could have happened i guess.
@GaryE- when you say they come individually bagged- do you buy them in box lots. that usually means you have to get 25 to 50 fish. I am curious how much you pay per fish, delivered when you buy 50 or 100?

Firstly, simply individually bagging the corys will not prevent them from excreting the toxin. It is handling the fish to get it into the bag that will can do it. As you will see if you read the sterbai paper I further down, the way they made the sterbai produce the toxin was to put it in a baggy with water and shake it. I do not care how one bags and ships fish, they will get shaken a lot along th way. The kicking merely induces the fish to emit the toxin so it is used up before they go into the bag. It is not inhumane. I figure a live healthy cory arriving is a lot better than letting it self poisoning along the way.

Before anything else I will post the title of the paper again as it may help people to know the paper is about:
"The Reversal of Self-Poisoning in"Bronze and Albino corydoras" So there should not be any reason for not knowing what species was involved.

Below is from Planetcatfish check out the synonyms.

Cat-eLog Data Sheet
Scientific NameCorydoras (lineage 7) aeneus (Gill, 1858)
Common NamesBronze Cory
Albino Cory, Bronze Catfish, Bronze Corydoras, Kobberpansermalle (Denmark), Metallpansarmal (Sweden), Panzerwels (Germany)
Type LocalityTrinidad Island, West Indies.
Synonym(s)Callichthys aeneus, Corydoras macrosteus, Corydoras microps, Hoplosoma aeneum

Subfamilies in Callichthyidae (by species)
2.Corydoradinae524 species(97%)
2.Callichthyinae17 species(3%)

The first Corydoras, the genus in the family of Callichthys, was discovered by Charles Darwin while visiting Buenos Aires during an expedition in the 1830 s and was introduced to the world in 1842. Subsequently, the Bronze Corydoras, shown in Figure 1, is a species in the Corydoras genus that were discovered to be scattered throughout South America, specifically on the eastern side of the Andes, Trinidad, and the shallow waters of the Rio de la Plata basin [2]. This distribution is exhibited in Figure 2. Initially pronounced Hoplosoma Aeneum by Theodore Gill in 1858 and eventually renamed as Callichthys aeneus [2], the Bronze Corydoras are well known for their armor-like exterior, ability to self-poison in life-threatening situations, and vibrant personalities that can light up any freshwater aquatic habitat [3].

So which of her references are not reliable? And slap her on the wrist for not saying sub-family or genera.

Next, it is nice to talk about single bagging. But when fish arrive from most suppliers in quantity, they will not be single bagged. In fact the only time I am aware of a large order of fish arriving singled bagged was when I and an associate imported about 328 zebra plecos from Indonesia in March 2020. The order included a few more fish for my associate and 25 of the zebras were for me. We bought 50 zebras of the large size (2 inch) and the rest (278) were 1.5 inches.

The price of the fish including and ancillary fees came to $40+ for the smalls and $72+/fish for the large after accounting for a few losses (of only the 1.5 inchers) suffered after they arrived. Our total order cost almost $14,000 of which about $12k+ went to the farm that bred the fish. The rest wenty for box fee, shipping and then paperwork when they arrived. My 24 zebras initially arrived in Chicago. My partner had to ship them to me in NY. They all arrived alive and were certainly not packed one/bag to come to me. However, the bagging was not done by hand when they sent the fish from Indonesia. There is a rather expensive machine that does the bagging.

Note in the vid they are not packing 1/bag..

Finally, I received a box with two bags a number of years ago. One bag held 15, 2.75 inch L173 plecos with one being DOA. The other bag held 99 zebra plecos with 3 being DOA. The box was shipped airport to airport from CA to NY. The fish were bagged for under 24 hours. The zebra bag was about 15% water and 85% air. I am reasonably sure that my supplier received the fish from a breeder in Europe. From the looks of the box they came to me in, I am betting my guy just refreshed the water and transshipped them to me. I thnk they arrived to him the same way he sent them to me.

How much do you think it costs to bag a fish? How long would it take you to bag my 50 sterbai corys individually? And if you are the boss, you don't do it, you pay somebody to do it. WetSpot will sell you Sterbai at 1.5 inches, live arrival guaranteed, for about $14 each. Are you willing to order a dozen or more from them at that price? Do not forget shipping is extra? That price includes bagging I am sure. And Wet Spot is the retail arm of the company. They also sell fish wholesale to resellers. While I did not buy them, some of my fish came to the person from whom I bought them from via the wholesale side of Wet Spot. Yjeor import arm is one of the biggest importers of a number of ornamental fish species.

The paper I linked to above as well as the one I am about to link were written by students as part of what was required for them to earn their degrees. Both were done with oversight by Eric Thomas Ph.D. He actually organized the sterbai paper by recruiting students interested in doing the research. Also note that 4 Ph.D. scientists approved the paper.

Wictor, E.P., 2020. A Proteomic Analysis of Corydoras Sterbai Secretions and Tissues (Doctoral dissertation, University of the Pacific).
My appreciation goes to Dr. Eric Thomas for allowing me to work in his lab and the countless hours he has spent with me on my project. The growth that I have gone through under his guise as a graduate student has made me a better scientist and person. I would also like to
thank Drs. Melanie Felmlee and Jerry Tsai for their input towards my project and for comments on my thesis.

Btw- I finally got to meet Dr. Thomas at CatCon 2022 in Herndon, VA. He was one of the speakers. You can see his qualifications here:

I know enough about Eric Thomas to say I am sure he read the paper I linked in my intital post as he was the one who posted the info and links for it in The Forum on PlanetCatfish--> Taxonomy & Science News, Sub-Forum Non-dissertation student research sticky

Btw, Eric T. is a very nice guy. So if you want to ask him about self poisoning in corys I suggest you head over to PlanetCatfish (register if you are not) and then shoot him a PM asking about self poisoning in corys. Feel free to let him know I sent you. Tell him that Chris, aka twotankamin, sent you.

Finally- here is the peer review info for the publication in which the original paper I linked to was initially was presented:

Peer Review​

Journal of Marine Biology & Oceanography follow single-blind peer review system that includes reviewers are aware of the identity of the authors, but authors are unaware of the identity of reviewers. There are minimum four reviewers for each article in each issue.
Every submitted manuscript processed for preliminary quality check control check by editorial office followed by external peer review process. Usually preliminary quality control completes within 7 days and is majorly with reference to journal formatting, English standards and journal scope.

Sorry, but between you and Dr, Thomas- I will have to trust the good doctor over you. But maybe I am misjudging your qualifications. Can you PM me some links to the papers you have had published in peer reviewed journals. I would very much like to read them. And if not your papers, then how about you biographical information so I know what degrees you have and what institutions to which you are connected. Thanks.
Expensive Corys have arrived in plastic jars, one per jar, with some sort of absorbent material. My understanding is it's done to cover in case one of the fish in the lot still has not released the hormones. I should have been clearer that I'm not talking about farmed stuff from Indonesia, but wild imports.
I usually only buy 10 or15 fish, as I'm retired and living away from the action now. I have an entire box of those jars under one of the fishtank racks. I've never ordered 50 for myself.

@TwoTankAmin - that is a strong reaction there. No one should have to send you their CV. You're a respected hobbyist and so is Ichthys.
The sarcasm aside, I have no problem with you favouring the work of a qualified person over me, but bear in mind that even qualified peer-reviewed persons can disagree with, and obtain results that contradict, other equally qualified peer-reviewed persons.
For a purely anecdotal response to OP's question, I have 5 pandas, 5 julii and about a dozen pygmy. The julii have always been more shy (originally had 3 as didn't realise they needed groups originally, then added more), but the pandas are definitely more outgoing. They're less likely to disappear when I walk past the tank and encourage the julii out a bit more. The pygmies will also sometimes hang out with the bigger ones and swim around after them. I don't know if different cories have different personalities which is why I say it's anecdotal but just wanted to share my experience. Having a few different types also helps me keep track of numbers and any issues which is a little bonus.
We are living in an age of antiscience. I am a big believer in the scientific method. One of the best aspects of the scientific method is that is expected that over time science will change what it thought was how something worked because new science is able to show this to be the case. Another word for this would be progress.

The rate of discovery for the history of man is unique. For a very long time little changed. And then mankind got a lot smarter. I do not know the current statistics on this, but I remember a number of years ago the following.

If we took all of the discoveries made by humans in their long existence and wanted to find the mid point of them. That is when was it that we could say half happened before and half since, the line was drawn at about 1900. But this was a while ago and I am betting that the halfway date has mover forward in time since i first read about the halfway point.

Most current science is built on prior science, The new science either disproves earlier science and replaces it or involves the ability to make new discoveries, This is usually the result of having new methods for discovering things. We would not know about the existence of bacteria for sure until the invention of the Microscope. We could not know what was inside our bodies without cutting people open until we got X-rays and MRI and CatScans. Better tools lead to better discoveries.

There is such a thing as the scientific method. There are rules for what gets published as well. This does not prevent science from reaching wrong conclusions but is does allow for such conclusions to be replaced by more accurate ones.

When it comes to cycling what was known when I set up my very fist aquarium in Jan 2001 and what is know today a mere 23+ years later amazes me. First, it appears as if ammonia oxidizing Archaea likely play an important role in out tanks. We were not aware such they even existed until they were discovered in a public aquariums about a decade or so ago.

When Dr. Hovanec discovered that it was Nitrospira that processed nitrite to nitrate, he had no idea that about 15 years later it would be discovered that they can also process ammonia straight through to nitrate. And when I was a kid in the 1950s my dad had a small tank int the entranceway of our house. I know when he set it up he had no clue about cycling. No fish keepers back then did.

The one thing I know is still the case is that to keep a tank safe from ammonia, there are steps we must take to do so. And we know what these are and we know how to determine when a tank is safe for fish in terms of ammonia and the cycle. We know all of this because of the scientific method.

So I make no apologies for what I have said above. In this case, I happen to know some of the people involved. So I will offer this quote:
"Everyone is entitled to his own opinion, but not to his own facts." - Daniel Patrick Moynihan

BTW- for any memders here from America, you can hear Eric Thomas speak and you can talk to him about cory self-poisoning at this year's NEC weekend April 4-7 in Groton Ct. He is a very nice guy and will be happy to give you some of his time. Here is the NEC blurb for Eric:

Catfish Speaker - Dr. Eric Thomas

Eric started keeping fish around 1970, at about 8 years old. With his older brother Bill, Eric kept and bred mouth-brooding cichlids (Geophagus and several Lake Malawi mbuna including Labeotropheus trewavasae, Maylandia zebra and Melanochromis auratus), along with Steatocraneus casuarius… and convict cichlids (who doesn’t start with convicts?). Eric and Bill were members of the now-defunct TriCity Aquarium Society of Southern California. In college, Eric studied captive husbandry of vertebrates; with his mentor Professor Rudolfo Ruibal at UC Riverside, in 1978 Eric was the first person to breed the Budgett's frog Lepidobatrachus laevis in captivity. In Dr. Ruibal’s lab, Eric learned about and began studying skin glands and their function. Eric went on to earn a Ph.D. under Dr. Paul Licht at UC Berkeley, studying reproductive endocrinology and the influence of sex hormones on frog skin glands.

Currently, Eric is an associate professor of Biology, co-chair and director of graduate studies for the Biological Sciences Department at University of the Pacific in Stockton, California. Eric’s research is split between reproductive pheromone production Hymenochirus frogs and self-poisoning in Corydoras catfishes, and recently he’s started studying Microglanis bumblebee catfishes in Peru.

As far as I am concerned, if one wishes to challenge his, or any other current science, you need to do so with newer/better science, not with just an opinion. No the earth is not flat :rolleyes: :
Flat Earthers confirm round shape with costly experiment

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