Never tried Coleus in a viv myself, but according to
Coleus - Wikipedia, the free encyclopedia
"The plants grow well in moist well-drained soil, and typically grow 0.5-1 m tall, though some may grow as tall as 2 meters."
and in case your interested
Coleus "has very mild relaxing and hallucinogenic effects. Coleus has not been explored very much but has been known to have been used by the Mazatec indians of southern Mexico who have been using this plant for years for its altering effects."