Learn About Rummy Nose Tetra - as part of the expert series by GeoBeats. The Rummy Nose Tetra, a small Tetra, a little bit larger than the Neon or the Cardinal. Gets up to about two inches in length. It occurs in several different countries. It occurs in Columbia, and Brazil, and a sister species in Peru. This fish is a unique fish in the hobby in the fact that you can tell how this fish is feeling and how your overall water chemistry is in your aquarium by how bright the nose gets on the fish. So it is kind of like the Rudolph fish: The bright red nose, your tank is doing well. Not so red, your tank is not doing so well. It is also one of the best schooling Tetras, meaning the fish, fact that they follow each other all over the aquarium and just neat to watch the huge school of these fish in the natural habitat or in an aquarium. They do really well in planted aquariums, and again, not aggressive to other fish. So they make a perfect aquarium fish.