i picked up two of these to use in the place of the closed loop for energy savings and so far i am skeptical. the out put is more dispersed then the k4's but the direct stream seems weaker. saying that i have good movement throughout the tank and the reef crest setting seems to be kncoking detrious out of hidden corners so i think they are working well. they are very quite so far and programming master/slave units was a breeze. i will post followups in a week or so.