what's wrong with my cory cat?

They sometimes get lazy as they age.
 
My bronze corys settled down with age too. I think it's normal.

I have a really big one now, and he just sits in the same place all day, but he's really healthy- good color and a fat belly.
 
I had a pair of really entertaining (and hyper) bronze cory cats. They loved swimming together, and were almost never apart. Unfortunatly, one of them died rather suddenly, and the other has never been the same since. I'm going to try to find a couple more to keep him company :)
 
before adding any fish, i would think about maybe getting a larger or a second freshwater tank? you seem to be quite overstocked.

the neons and rasboras both like to have larger schools of 6 fish or so, maybe, pick one or the other and then enlarge their group (but don't keep the other kind). ditch the swordtails, loach, and pleco, or get another 10g. even dwarf plecos will get around 5 inches long. then add two more bronze cories to keep them happy. you would be borderline overstocked anyway, but it can be alright with good water changes.
 
AquariaCentral.com