I have a 42g Brute trash can that I use to store my bulk ro/di water and have a k4 in it that does a good job. i have a mag 7 in my 32g saltwater brute trash can. in my two salinity buckets i have next to my tank for top off i do not have any powerhead, i also use about a gallon a day. and now that i have and ato i only check once a week.. plus i have connected the two buckets so i only have to fill one bucket up and it fills up both, same for when using water.. only take from one bucket.