Freshwater angelfish can sometimes be shy creatures, especially when their environment changes, either through redecorating the tank or moving them to a new one.
Tetras, on the other hand, enjoy swimming in the open. So I enjoy adding tetras to my angel tanks as a signal to the angels that all is well and it's safe to come out and play. They have a calming influence on them.
These are unlike some tetras that gain their color through inks that are injected or dipped in dye - barbaric processes that kill many fish and compromises the others' immune systems.
So how did this fish get its fluorescence?
The process was originally developed by scientists who wanted to develop a fish that could detect toxins in the water. The original fish were modified by a gene from a jellyfish. To get other colors, genes from sea corals or other variants of jellyfish are used. The result is a breed that can reproduce fish with the same fluorescent colors.
The first fish to be introduced into the aquarium trade with this characteristic were GloFish, danios that had been genetically altered from their silver and black stripes to shades of yellow, green, red, blue and purple. Now they are becoming available in the tetra line.
My electric green tetra (I have six on one tank and six in another) originated with the long-skirted white tetra to which a jellyfish's genes were mixed. They get along great with other tetras and with my angelfish. They are very peaceful and tend to school. If you get any of these fish, you'll want to get at least three, as they become very shy when they are not with others of their own kind. I have them paired with other tetras so I have a school of 12 to 15 in each tank.