Now that the NG has convinced me that it's wise to have a bottom drain
[thanks all!] . . . .

I'm thinking of using the Biofalls (skimmer and the waterfall part). The
pump sits inside the skimmer. Question is, where does the outlet of the
bottom drain go?

Is the drain under suction all the time (e.g. plumbed into the pump or
skimmer somehow), or do I just use it to suck the gunk out every few months?

Thanks in advance!