Paracheirodon axelrodi or cardinal tetra is like Angels one of the most desired fish to have in a tank. So far, in my tank there are 20 fish of this species. Eventually this group has to grow to approximately 50 fish.
The cardinal tetras in the tank are being kept company by 5 rummy-nose tetras.

"Keeping these little fish requires a certain knowledge. These fish are extremely hard to breed in captivity, virtually all of the fish available in shops have been taken from the Amazon basin, and unfortunately thousands of them die every year in inappropriate tanks.
These fish are actually quite hardy, as long as they are properly adapted into captivity. First of all, they are very sensitive to changes in water parameters after being caught, so the water should be kept as close as possible to their natural habitat. Second, they should be kept in large numbers (at least 5, many more if possible) in a well planted tank with lots of shades and hiding places. This greatly reduces the stress that leads to many of the deaths. Needless to say, their tankmates should be peaceful and preferably small. After a while in these conditions, the cardinals tend to become more healthy and confident. They don't bother to hide anymore and become much more tolerant of changes in water conditions."