Extremely cold water peppered Cory cats

Hello everyone I'm new to this site and came here in search of answers to something bizarre .
I've been keeping fish most of my life and have kept a wide variety of fish over the last 40 years and also worked in a couple of tropical fish hatcheries and in a few retail stores until I changed career paths.

All that being said I recently observed something that shouldn't be possible.
I had a bad algal outbreak in a 20 gallon community tank in which I have 3 mid sized Pepperred Corys . I had a bunch of Rotala Indica plants that were overrun with algae . So I decided to take them out and put them outside in my fiberglass pond to let some snails and algae eating crustaceans do their work and devour the algae since my shrimp hadnt done their jobs.
The water was very cold as fall had come and night time temps dropped down to 40 F. Weeks later I was snatching up some blood worms from the pond to feed to my fish when I noticed something small swimming at the bottom of the pond. My initial thought was that it was some small tadpoles but it didn't make sense because nothing I knew of laid their eggs in the Fall .

So out of curiosity I netted a couple of these small critters up to get a closer look at them .
To my shock I saw barbles ,gills and fins after looking at them with a magnifying glass .
I said to myself "No that's not possible for a Cory cat to have their eggs hatch in such cold water ". Yet there they were showing me otherwise . Right now I have 11 tiny catfish swimming about in a small aquarium I transferred them to in my garage where the temp is at around 55 degrees and they're happy as can be .

I've documented this as best I can but I'm still in total disbelief that this is even real ! From everything I know and have read through the years this is not possible . Sure I've heard of down to the mid 60s but not the mid 40s ! When I filled this pond it was cold tap water from a deep well .I then tossed the plants in there and pretty much forgot about it for a while until I saw this. I've identified the babies as Cory cats for sure and nothing else .

So my question to anyone who knows about catfish is how is this possible ? Unfortunately I did find others that didn't hatch but just the fact that any hatched at all and even survived totally amazes me . Ive shown people that I know this rather odd but amazing observation I've made but others who haven't seen it with their own eyes are quick to judge and say I must be lying . All I can say is seeing is truly believing . To me it just proved to me that mother nature is far more complex and mysterious than I thought possible . If anyone else has information regarding this matter or how this is possible please by all means send me a reply .
Thanks
Michael

Hi and welcome to the forum

Corydoras regularly live in water that is cool 10-20C (50-68F), so dropping down to 40F isn't that much of an issue for them. All fish have the ability to adapt and some fish will tolerate cooler conditions better than other fish in the same batch of eggs. Chances are you got a group of babies that are more temperature tolerant than the others that didn't hatch or hatched and died.

This is a natural survival mechanism that allows a species to tolerate more variable conditions. Fish can produce hundreds of eggs in each batch and if 1% of them can tolerate colder water than the others, it gives those fish more chance of surviving in cooler environments. And the more temperature tolerant the fish is, the more chance of it surviving in different environments.

I had a number of rainbowfish (Melanotaenia praecox and M. trifasciata) that I was breeding. I put batches of eggs outdoors in ponds. In summer the ponds hit 40C+ (104F) and in winter the water dropped to 5C (41F). Within a couple of years of working with these fish I had strains that could tolerate temperatures from 5-45C. These are tropical fishes from northern Australia and New Guinea, yet they were able to be kept outdoors in the cooler parts of Australia all year round. We also had strains of Pseudomugil mellis and Rhadinocentrus ornatus that we were producing and they also lived outdoors all year round and were tolerant of the same temperatures.

All fish have this ability and if you keep those particular fish and breed them, you can increase the temperature range they can live at.

On a side note, I kept all my Corydoras in unheated tanks over winter and the water dropped to about 15C (60F) for several months before it starts to increase in spring.

C.paleatus originate from Argentine and Uruguay and therefor is known to be a cold/coolwatercory.

This is one of the only corys that can be kept in ponds in our region

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Thanks for the thoughtful response on this subject . I know that fish can adapt to a wide variety of conditions but this just blew me away . I didn't think it was possible for a tropical species to be able to adapt to such an extreme temperature . I looked through my various ichtheology books and online for information but couldn't find anything to suggest that this was possible .
Well I guess you learn something new every day- right ? I recall a time when I had some paradise fish outside in a pond for the summer and then got sidetracked with girls at the time ( teenage years) lol
Anyway I had forgotten about them till the pond iced over about 2 inches thick .I immediately thought of them and thought "Oh no they're going to be dead ",and felt so guilty
However after breaking the ice and searching around for them ,I found them alive and well although in a sort of hibernation mode .I took them out along with the same water and just let the temperature come up slowly and they were happy as could be , lived long lives and produced lots of babies . Then again paradise fish are well known for their toughness . I guess I can put those Cory cats in that same category .
Once again thank you for your response . I got flamed at another forum I had been a member of for awhile with people saying that I was making it up and some outright insults I won't mention . Sometimes people get upset when you challenge the accepted wisdom I guess. One person said thats impossible and you're a liar .My response was tell the fish it's not possible !
Well anyways it's good to see civil responses by real hobbiest .Have a great day .

Michael1970 said:

Thanks for the thoughtful response on this subject . I know that fish can adapt to a wide variety of conditions but this just blew me away . I didn't think it was possible for a tropical species to be able to adapt to such an extreme temperature . I looked through my various ichtheology books and online for information but couldn't find anything to suggest that this was possible .
Well I guess you learn something new every day- right ? I recall a time when I had some paradise fish outside in a pond for the summer and then got sidetracked with girls at the time ( teenage years) lol
Anyway I had forgotten about them till the pond iced over about 2 inches thick .I immediately thought of them and thought "Oh no they're going to be dead ",and felt so guilty
However after breaking the ice and searching around for them ,I found them alive and well although in a sort of hibernation mode .I took them out along with the same water and just let the temperature come up slowly and they were happy as could be , lived long lives and produced lots of babies . Then again paradise fish are well known for their toughness . I guess I can put those Cory cats in that same category .
Once again thank you for your response . I got flamed at another forum I had been a member of for awhile with people saying that I was making it up and some outright insults I won't mention . Sometimes people get upset when you challenge the accepted wisdom I guess. One person said thats impossible and you're a liar .My response was tell the fish it's not possible !
Well anyways it's good to see civil responses by real hobbiest .Have a great day .

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I'd only do that with Peppered !!! Those are the less tropical of all Coryspecies. Kept as one of the first. Have one in my book from 1925!!

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DoubleDutch said:

I'd only do that with Peppered !!! Those are the less tropical of all Coryspecies. Kept as one of the first. Have one in my book from 1925!!

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Ive been keeping these for many years , they are a brilliant Cory . : )

I keep like 6 different species. I'm very happy for you! I'm surprised none of your fish ate them in the pond. Well they also had a lot of micro organisms to feed on as well.