New Factor on my Congo Tetras?

[cupofjoel]

This may not be good news!
As @essjay suggests there is a difference between shoaling and schooling species. Many people don't recognise this difference and use the terms interchangeably. I don't keep congos but most of my tetras only form a tight group when they are stressed or frightened, like when my cat tries to catch them through the glass . The fact that they initially "schooled" and after a couple of weeks relaxed enough that they were happy to explore on their own suggests that this may be the case with these. If this is the case it means they are being stressed by their tankmates.

I guess I should have clarified. They went back and forth from schooling and doing their own thing individually. Hope that helps.