Hey there,
to make it short:
"We will then have a closer look at a different point of view - that is, (bla bla bla)."
I happen to use this kind of phrase a LOT..
So my question is this: Do I have to put a comma there behind "that is", or may I leave it out...OR would it be completely wrong if I didn't have a comma there? Should I go for a colon, maybe?

Please help me. I know it's a minor problem, but I gotta solve this one before the end of the week, since I have to stick to a deadline if you know what I mean, haha.
All the best