SLEngst wrote:

I have a new Filstar XP2 in a 55 gal. heavily planted tank. The design is
intended to have the outfall at the top, on the same side of the tank as the
intake. This can be easily changed by getting some extension pieces. I'm
making the assumption that I want as much water circulation (without disturbing
the surface) as possible. Would a better outfall location be the opposite side
of the tank, at the top, or along the bottom?

If you inject CO2, you want to MINIMIZE surface agitation. Many of us put the
outflow a bit below the top, pointing down, but it depends on tank layout.

If you do not inject CO2, you want to MAXIMIZE surface agitation. Put the outflow
right at the surface , pointing horzontally to stir things up nicely.