5 Three Lined Pencilfish - Don't School

[Alps]

My friend has 5 of these, 7 cardinal tetra, and 2 bolivian rams in his 20 long and they don't school at all. One of them has his own territory and the rest just stay in their own spots, they aren't even social like the cardinals. Whats the problem with his pencilfish?

Thanks

 

[Alps]

Don't know how many of you have pencilfish. Don't seem very popular, but anyone with any input would be welcome.

 

[ulster exile]

I have 4 golden pencils (looking for a few more though) and have noticed that they mostly spread thoughout the tank.

Maybe it's a sign that they're comfortable in there as most schoaling fish schoal when they feel threatened?