Cory Problem

[Booswalia]

Hi,
I've had two cories in my tank for about 5 or 6 years and they've always done well. They usually hang around the bottom and occationally make a dart for the surface, but not very often.
Lately, they've been hanging around the surface almost constantly. They don't appear to be sick or anything.

It's a planted tank and the only thing that has changed is that I added a few new plants; some cabomba, and some ludwigia. Ph is 6.8, nitrates are 20 and the other fish seem fine.

They seem to almost stick their heads right out of the water at times as if they were gasping for oxygen, but there's plenty in the tank, I'm sure with it being that heavily planted.

Any ideas whiat might be happening to them? Could it be my substrate?

Thanks for any ideas.

Shirley

[ChilDawg]

It could be your substrate. I wonder how anaerobic conditions are in it!

[VoodooChild]

Chil's gotta point there. Otherwise, the only reason they'd be doing it is if their gills were damaged. Did you cycle the tank initially with them? There could still be damage from way long ago. Otherwise 6 years is a good run for a cory. It's odd that they're both doing it, but they could just be oldies.

[Booswalia]

It may be anaerobic because I do get a few bubbles when I poke it with a chop stick, but it's been like that for year.

It has me baffled because I moved one of them to my other tank which has only been set up for about 3 months and he is still hanging around at the surface.

Shirley

[Mantis_22]

cories have the ability to store air pockets in there mouth beside their gills if oxygen is needed for them. I have 2 in one tank and they did it daily. They tank wasent aerated though. So its either something new in the tank if they just started doing this or the substrate as said...