i have two #1's in my 55. they have a really good flow to them. even though they have a much wider flow than a normal powerhead. it seems to be more of a multi-laminar flow rather than evenly distrubeted wide flow. this can be noticed if you hold the powerhead in you're hand, aim it at something, and slowly rotate it. you will have one area with a really strong flow, and 180 degrees from that spot you will have another area with really strong flow. but, i still like them a lot. it just takes a little tweaking to get them right where i want them, to keep the sand from blowing up in one area, and not having much movement in another.