RE: What fish would you recommend for a beginner who wants an aquarium?
While most Corydoras catfish are fairly easy to take care of, not all of them are equally hardy since there are many different species of them. Some of them such as Panda Corydoras, and Albino Corydoras catfish are more fragile in comparison to other Corydoras species.
Yes, I think Corydoras in general are very cute. It is required to have minimal 5~6 of them for a school. Any lower number will cause them to be shy and stressed, and they will hide most of the time. When they are high in number, they will be very active and digging around the aquarium substrate searching for food, or chase each other around for fun. The average life span of these adorable little catfish is over 20 years if you take good care of them. To get the best out of them, it is recommended to have a fish tank of minimal 30-gallon in size. Any smaller sized fish tank will limit their level of activity.
One good thing about these corydoras catfish is, they are bottom feeders. Not only they won't bother the fish that occupy other water level in your fish tank, they will eat the leftover fish food at the bottom of the tank. Who does not want free cleaning service? It is one of the good ways to keep the water quality high, although you still can't skip regular aquarium maintenance just because you have bottom feeders.