Now THIS is a tetra! Full bodied, fins that look like lace, iridiscent sheen... they've got it all. Truly beautiful! I bought some babies almost a month ago, and they're growing quickly on a diet of meaty foods, flake, shrimp pellets and algae wafers. They eat it all, and very readily. They're peaceful, and love a school. They are not well-suited for small tanks because of the adult size of the fish, and the fact they require a school to be happy. One thing I've noticed that's really neat is they have TEETH! Big ones! Most fish have teeth, but they're not usually large enough to be seen, especially in juveniles. If you're looking for a centerpiece fish, but want something peaceful and beautiful, you can't go wrong with a school of Congos.
I had a Congo Tetra in my Community tank. She was a little aggressive with other members of tetra family for example she will pick on bleeding heart tetra, red-eye tetra, black tetra and neon tetra. What I realized is that, next to neons, Congo tetras are very delicate when it comes to the condition of water. One time I was changing the tank water and forgot to use chlorine remover, within minutes I lost my neons plus my Congo tetra. It was a mistake that I will never forget. All my other tetras survived this 10 minute ordeal. Even my Rummy-nose was hardy enough; but the congo tetra turns out to be too sensitive to water condition. Congo tetras are relatively fast swimmers, compared to other tetras they need at least 80 liters of tank, plus the tank should be well planted. Congo tetras are not for beginners, this fish is for true tetra lovers. The metallic green color of this fish catches the eye of advanced hobbyists. This fish is a true beauty in tetra family. To start with tetra family, the best choice is the black tetra and work your way up to Emperor and Congo tetra.
I have a school of five young ones, 2 males and 3 females. They live in a 200 liter community with 4 columbian tetras, 3 bleeding heart tetras, 2 emperor tetras, 2 large anglefish and some others. My water is very soft and the pH is around 7.0. The temp stays around 27°C. I love my congos, they school with all the other tets in my tank, usually hovering under a large piece of root in the center of the tank. It's also a very shaded area of the tank and really shows the tetras off. My congos never went through a shy period, they fit right into the community.
I also purchased congos from WalMart and developed a love for them. I got 2 males and 9 females, but at $1.19 (listed as "misc tetras") each. Even females are prettier than a lot of fish. They were energetic, worthy fish for a planted 200 L like mine. They mixed beautifully with Giant Danios, Kribensis, Angels, Serpae Tets and Spotted Raphael Cats in my "Jungle" aquarium. Mine never were observed breeding, but I had plenty of Java Moss and Hornwort. Due to the incredible monthly color swings I assume they had spawned, and like dumb egg scatterer had a caviar meal along with my Serpaes. Darn good fish.
There are already lots of great comments about these tetras on this site that I won't duplicate or contradict. Only quirky sort of thing I'd add is they love to eat smaller-size house spiders! Ounce for ounce, the trout where I dry-fly fish don't hit the water surface nearly as hard!