I know these aren't darts, but they are similar. I have six golden mantellas that are in quarantine right now. I put them in a horizontal twenty gallon. After a few days of observation I noticed they loved to climb and mainly hung out on the upper parts of the tank. So I just decided to experiment and changed around their temporary tank to a vertical instead of horizontal. Within an hour of putting them in their new vertical tank two males start calling and two usually shy females were much more bold. I'm currently making a permanent viv for them, and am thinking of making it vertical. Thoughts?