I think I read somewhere that Pencil Fish can live up to 5 years...they do will in 72-84 degree waters ~ here is a link that has additional info
http://animal-world.com/encyclo/fres...Pencilfish.php
Also found this:
"Discus in general of course always do better on their own. But aquarists from all around keep in them communities often. Both Angelfish and Discus are cichlids which exhibit territorial and aggressive behavior to some extent. But this is normally directed at other fish of the same species. Keeping both these fish in large groups of four to six should limit aggressive behavior. I mention this because there is much controversy about keeping angels with discus and I think the key to this is keeping both these fish in a school so they can keep to themselves instead of bothering the other fish. Nearly all tetras should make excellent companions, as do small to medium south american catfish, such as bristle nose plecos, royal panque, as well as the well camaflouged royal farlowella, other S. American catfish like Banjos and the beloved little Corydoras are excellent for a sout american biotop tank. Tetras like the red-eye, Cardinal, neons and the like are excellent. The highly interesting pencil fish such the dwarf and Beckford's pencilfish are also amazonia species. Don't forget about Hatchet fish, and the unusual penguin fish whom is a also part of the pencil fish also is from the amazon. The key is the pick only peaceful fish whom mind their own business and to research any specific species before purchase to insure you can provide their proper care and can know what to expect from their temperament. Another very important procedure when keeping discus with other fish is insuring you quarentine all new arrivals since discus are suceptable to any parasites or diseases the new fish may bring in."