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I decided to keep three C. paleatus in an umheated tank. This morning (about 7:00 AM) I checked the temperature of the tank, and it was about 57-58 deg. Is this too cold for the fish?

Check the paleatus profile right here http://www.planetcatfish.com/catelog/sp ... ies_id=271
It looks to me as if you got very lucky to have a cory that can go very cold without damage. According to their profile, you are just outside their acceptable temperature. I would not leave them that cold for very long at all.

Kets wrote:I decided to keep three C. paleatus in an umheated tank. This morning (about 7:00 AM) I checked the temperature of the tank, and it was about 57-58 deg. Is this too cold for the fish?

It is a subtropical species, so that is actually a good winter temperature for it.

My Corydoras are wild caught in southern Uruguay. They have spend 3 winters at 10-14 degrees C, but this winter is a bit colder, 8-10. However, in autumn I got eggs, and the fry, 1 cm, is having the same temps, without any problem

As far as I know, 10 C is 50 F, 8 would be 46

I don't bother loking in any table about them, the only table I use tells me about the wheather. The average form 2001 to 2008, for the average dayly temp in july is 10,2 C

So 10 C, without any day lower, is actually quite a mild winter for them (I collected them in small creaks, with 50 cm water or less)

So, don't worry

Thanks! I knew that C. paleatus was cold-hardy, but I just wanted to make sure.

It seems to me, I could very well be wrong, that even cool water fish need a heater in the tank set to their lowest likeable range in case for some unknown reason the temperature outside or inside the fish room decides to drop lower then that. Seems like it would take away any worry re your tank dropping too low.

FWIW I've kept paleatus at 4 celsius (39F) for over a month with no apparent ill effects, and my guess is that they'll survive down to freezing.
Like most fish they stopped eating when temperature fell under approximately 8 celsius (46F).

But, if I may ask, why would you have them that cold. And are these tanks in the
House? I am just confused why are they getting that cold. I mean aren't these tank raised
Peppered cories? I can see very low 70's or high 60's. I realize I am relatively new to cories
But mine liked low 70's.

Was the drastic temps in each posters case an accident or a surprise
Situation?

As stated, mine were collected in the wild

I reserve a room for them where the window is always open - or partly open if it gets a bit too cold - in order to provide the fish from Uruguay with a good winter.

So the cold is intentional, as I know they'll need it

I had thought my basement was in the low 60's, so it wasn't intentional.

andywoolloo wrote:It seems to me, I could very well be wrong, that even cool water fish need a heater in the tank set to their lowest likeable range in case for some unknown reason the temperature outside or inside the fish room decides to drop lower then that. Seems like it would take away any worry re your tank dropping too low.

Although fish able to survive 8 C in-house will be hard to die from exposure, in fact I would like to keep them outdoors.

I do have a few ponds, covered with insulating glass, but I would need a tank heater adapable to 6 or 8 degrees C, which does not cost overly much, and has a capicity of no more than 200 watts (7 ponds, with 2 KW each might blow away may plugs at 10 KW if they all start heating at the same time)

Normal tank heaters will not go below 17 -20 C (depending on the brand)

wow, that just seems so incredible.

Thanks for explaining it.

andywoolloo wrote:But, if I may ask, why would you have them that cold.

They were company to another fish I was trying to breed, and which I thought might need cold overwintering to spawn. 4 celsius was my guess at a suitable temperature for the other species, and the peppereds tagged along.
Also I had it on good authority that in the southern parts of their range peppereds live in waters which may briefly have ice, so I was pretty sure they would survive if acclimated slowly.

EDIT: My peppereds were bog-standard store-bought ones, the "classical" paleatus type with low dorsal fin. Here's a picture of one of the males.

He is a beauty!

In correspondence with a friend in the UK recently, he told me that his Corydoras paleatus and some Austrolebias alexandri were doing fine despite the inch of ice covering his outdoor ponds, so as Bas has said, they are well adapted to cool water and your basement low temps are well above their minimum requirements.
I was surprised that either species could tolerate such lows and astonished about the annual killies but then again, their ranges overlap.

Perhaps I'll have to keep some Corydoras outdoors next year

Luckely I do have some F1's

apistomaster wrote:Corydoras paleatus and some Austrolebias alexandri were doing fine despite the inch of ice covering his outdoor ponds

Astonishing. Presumably the higher oxygen content of cold water and the lowered metabolic rate meant the Corydoras could get sufficient oxygen from the water, and didn't need to go up for air?
You wouldn't happen to know approximately for how long the pond had ice cover? Just a ballpark figure (a week? a month? two?) would be very interesting.

Mike,
I know it happened this winter so you are probably more familiar with the cold snaps that occurred over there than I.
I wouldn't assume the ice cover was 100% air tight.
It seems reasonable that the fish 's metabolisms were in slow gear in such cold water and that the ice cover did not last long enough for O2 depletion to be very significant.