Update
I noticed that the corydoras I have are really picky eaters. They seemed to not like/ignore/spit out the flakes I've been feeding my tetras and gouramis. I dropped some algae wafers in there, and it stayed in the tank overnight. Thank god it didn't mess up with the water. Then I started feeding them hikari sinking wafers (not the algae ones) and the sinking carnivore pellets and they seemed to accept those a bit more. The corys would find the wafers, munch on it for a bit and then look somewhere else for food. My next step was to get shrimp pellets. The wardley ones are horrible; it almost instantly disintegrates in water. And the corys reacted indifferently to them and ignore them most of the time.
At this point I was all worried that my corys would starve to death sooner or later.
All of this happened UNTIL I stumbled upon a thread (in another forum) that addressed this issue. One of the repliers stated that he has been feeding his corys the hikari frozen-dry tubifex worms. The problem is, that frozen dry worms/food never sink and corydoras almost never eat from the surface. The way around this, the poster found, was to attach plant weights to those worms cubes and let them sink. So having read this, I decided to give it a try (I already had this food in my big stack of fish food that I have)... and it WORKED. All my 8 corydoras go crazy after the tubifex worms including the tetras. The gourami doesn't seem to like it that much, which is good since he has been pigging on the wafers that I drop for the corys.
As a result, my corys have changed from a lethargic state to a more active one, swimming and chasing each other around the tank - the normal healthy behavior that i was looking for.
PS. I'm assuming that they would react in a similar manner to frozen food (not dried), but I have never given them a try.
