To your initial question, you're fine. Corys are "substrate" fish, true, but most species (and C. panda do this much more than some others) will spend more time off the substrate, browsing every surface be it plant leaf, wood, or tank walls. But of the several species I have, they seem to remain together most of the time. My group of five have taken a real like to playing in the filter stream periodically; probably not surprising, since this species is native to slightly faster-flowing clear water streams coming down from the Andes.
That tank looks very nice Patricia.:cheers:
I agree with Ed on sand, but if the gravel is not rough you should have no issues. Corys do like to sift sand through their mouths, ejecting it via the gills, which they obviously can't do with gravel. But though I have now changed to sand, I had corys thrive over natural gravel for many years. I mentioned their habitat above; those streams have substrates of sand and/or fine gravel. Just so long as the gravel is not rough, you're OK.
Byron.
