Cory Cat's are a widely popular type of catfish in freshwater aquariums. These fish are interesting to watch and they are nice to have in the tank. Most people enjoy the Moon Cory Cat's (Corydoras Adolfoi). I always like to keep several of these in my tank and the not only add to the beauty of the tank but they have many interesting charicteristics. They are also a very hardy fish.
One of the things that's not so well known is that some Cory Cat's are nocturnal and they are nocturnal because it's safer than being active during the day. This all comes to them by instinct from thousands of years of evolution. If they eat when all of there predators are sleeping then they are in much less danger. This is one reason why you shouldn't leave the light on constantly.
Some people may wonder why they sit between two things such as plants or two rocks. The reason they do that is it is a hiding place from predators and it gives them protection. You might be able to eliminate these hiding places in order to make the Cory Cat more visible and possibly more active but if you eliminate these hiding places it will cause stress on the fish and stress could lead to sickness and problems.
Cory Cat's are bottom scavengers so they eat what ever flake food falls onto the gravel. For my Cory Cat's I have pellet food which can be bought at the local pet store. I simply drop it into the tank whenever I do regular feedings and by morning it's usually demolished by the Cory Cat's. The pellet food is better because they will always get some food that won't get eaten by the tankmates before it reaches the bottom. The pellets are also made for cory cat's and will be more fit for them.
Be sure that when you change your water you use the gravel cleaner that sucks the fish poop out of the gravel. You need to clean the gravel about once every month or two. If you have any type of catfish you need to do this for them. It will help prevent disease and stress on the Cory Cat's. As well as helping the Cory Cat's it will also improve the water quality by having less rotting matter in the tank. How would you like to pick your food off of the ground covered in poop?