Upside down Corys

[Stoll77]

I just setup a 90 gallon freshwater the other day and I put 5 corys in it yesterday morning. When I came home in the evening after a softball game, 3 of them were floating upside down at the top. As I reached in with a net to take their lifeless bodies out of the tank, they all swam to the bottom and started acting completely normal. I tested the water and the ammonia was a little high so I did a about a 30% water change. They have been fine ever since. I don't believe this is normal behavior but I could be wrong. Were they eating something off of the surface possibly?

[VoodooChild]

It's possible they were eating but you would notice it. Other possibilities include their gills getting burned by the ammonia, hence the need to rise to the surface to get more oxygen. Otherwise they may have swallowed air, some how, and either have it blocked within them or are passing it through, though I've only seen this in goldfish. Either way, they lack swim bladders, in a sense, so it takes alot of effort for them to stay afloat. Keep on eye on them and try to get the ammonia to drop.

[OrionGirl]

Cories are very sensitive to ammonia. Anything detectable by a hobbyist kit is enough to burn their gills. Burned gills means they have a hard time getting sufficient oxygen from the water, so will resort to gulping air from teh surface. In extreme situations, they will stay at the top to stay alive.

I take it this is a newly setup tank? While I prefer fishless cycling, or using media from an established tank, cycling with fish can be done with minimal damage to the fish. However, cories are not a good choice for fish to cycle with, and yours will likely not survive. Sorry.

[anonapersona]

If this is related to cycling, you can skip the whole thing by adding Biospira, expensive, but worth it, or so I've read from those that have used it.

[ChilDawg]

Not to flame but merely to ask: Can you use Bio-Spira after the introduction of fish?

[famman]

yes you can use bio-spira after you add fish. there have been sufficient postings to lead me to believe that bio-spira actually does work when fresh.
good luck
:)

[Matt W]

I read somewhere that cories always keep their bellies to the nearest surface...even as far as to go upside down when the water line is the nearest surface....

let me see if I can find that article...

hmmm..can't seem to find it...will post if I do...

[SBA]

i have peppered cories that 'go upside down' when feeding at the top of the tank in the floating plants (although trilineatus don't seem to do it), but you know they are feeding - they don't stay still.

[ChilDawg]

Thanks, famman! I was just making sure for my sake and the sake of the poster. :)

[anonapersona]

I believe the answer is yes, as this has been suggested in other fourms after medications have trashed the biofilter and the tank was likely to begin a new cycle when full of fish. I recall someone testing it with fish in an new tank with a few very large fish also, but heard this second hand or third, so I can't vouce for it for sure.

But, best to check with someone who actually knows for sure.