So I've been reading up on closed loops, looking at powerheads online, thinking, measuring, and getting more indecisive the more time I spend thinking about creating a plan for my 120G. Where I'm at right now: I have a running 57G rimless with a mag 9.5 and 2 1/2" Sea Swirls. For the 57G, this worked fairly well. I couldn't ever turn the pump all the way up because water would push up the side, and with no trim on the tank it would collect on the rim and drip over. It also tended to dig out the sand in the front corners, but that diminished as the sand aged and settled. I was reasonably happy with this setup, but I would put it right around the minimum amount of flow for that size of tank without having serious dead spots. The major problems I had with this setup is that the vast majority of the flow is pointed straight at the glass, and only hits the corals obliquely. In addition, with the sea swirls, there is no "cumulative" flow effect such as a gyre or circular current. This leads me to think I'm going to need more flow in the 120G. I have an extra mag 9.5 I bought on sale as a backup, so in some ways I'd prefer to set something up with what I have. I also very much want to stay away from having powerheads stuck all over the new tank. I thought about sticking eductors on the sea swirls and moving to a pressure rated pump, which would help move more water, but would create a stronger jet pointing at the glass and bouncing down it into the sand. Kind of nixing that idea for several reasons, partly because it would add more mass right in plain view on the sea swirls, and partly because I just don't think it's the best solution. I then started thinking about using a closed loop. I've never done one, but they seem fairly simple to plan out. However, I wanted to add a wrinkle to mine, in that I was thinking of putting the outlets in the front corners of the tank. I could disguise them by drilling some rock or just sticking it on the outlet with cement until I was happy with the look, and from the front it would look like a normal rock, and eventually I'd grow an encrusting coral on it. Where I'm stuck is in how to aim them, my original idea was to shoot water at the rockwork, from the corners inwards towards the center of the tank. Then I thought maybe a gyre would be better, and then I thought hmm maybe I should just do two closed loops, one gyre on a long on off timer, and one with outlets pointing at the rockwork. Which brings me to the problem of finding a pump that can run a closed loop and handle an on off cycle. I was thinking of the gyre being a 3 or 6 hour timer, and would like to go with a fairly short timer on any outlets pointed at the rocks. I know the mag pumps won't work on a timer, they cavitate like crazy on startup. Has anyone done something like this? What were your experiences and do you guys have any suggestions? I realize I'm kind of creating a possible tank failure by putting the outlets of the closed loop low in the tank, but I've seen many closed loops with suctions placed low, so I am thinking it's not a huge issue? Any input is appreciated, especially in the planning stages.