Hi, I am using MP40w for my 2 feet cube tank.
What I learnt from the expert is that MP20 could be too weak for use in my tank.
Currently, I am using about 3/4 strength for my maximum long pulse mode;
you can see the wave on the water surface.
And if I am having a 3x2x2 or a 4x2x2 tank, I prefer having one MP40w and one MP20
coz, I think one can be master and one slave and they move in tandem; something like that.