Well, you don't want to leave it running non-stop; if you do, you run the risk of adding extra kalk that's held in suspension. Just mixing a few times a day is fine.
That said, I'm using an Eheim 1250 to mix mine. I just realized that I've worn out the impeller after less than a year of use. The plastic shaft that runs up through the middle of the impeller (that the blades clip onto) has worn down enough to make start-up unreliable (and it rattles badly when it does start up). The impeller is a $30 part (plus shipping) on a $75 dollar pump :-(