I have a six ft tank, Yes, I use two of these and like them. The fact that they plug right into apex and don’t take up outlets is nice. They are highly programmable through your apex too. I’ve had mine for nearly two years and no issues. They do push quite a bit less water when they need to be cleaned, but that’s true for all pumps.
I also run a gyre to really move water, but the WAVs really help to randomize the flow. I think two WAVs are a great choice for a 4 ft tank, especially if you already have the APEX.