The Cories are Listless, not a gary larson tale...

[VOTE]

A few days ago, I noticed one of my four Albino Cories had ceased moving so erratically, and instead rests at the same spot on the bottom. All four Cories now do this, but do varying degrees. For instance, only two appear to be breathing heavily, and only one is so listless as to not leave his spot beneath some driftwood.

I know Albino Cories are 'early indicators', so any ideas as what they're suffering from? Is it contagious? Remedies, etc...

Prepare to be hit by the digits:
75 gallons @ 79* degrees
ammonia, nitrites and nitrates all within acceptable parameters
10 Buenes Aires Tetras
6 Pristella Tetras
6 Black Skirt Tetras
3 Danios
3 Otos
and the 4 Cories

I recently removed a piece of limestone in hopes it would alleviate my listless Otos, and it seems to have worked. The Cories became listless after this - any chance this change in water parameters is what's affecting the cories?

Thanks

[TKOS]

You say ammonia etc... all in acceptable parameters. I assume that means 0 for ammonia and nitrite as that is the only acceptable parameter. Nitrates should be below 20 ppm. Has there been a large shift in pH recently after you removed the limestone? Perhaps they are just adjusting to the new layout and are a little confused.

Cories need a good clean substrate. Are you using a gravel vacuum when you clean? And what do you feed them? How long has every thing been setup?