Powerhead placement help!

[Snoopeeyy]

I'm beginning to put together my 20 gallon long reef tank but i want to make sure the flow mimics that of the ocean per say. I have 2 Koralia 240's and 1 Koralia 425 but i only need to use 2 PH's. Which is a better combo and wher should i put/face them for the best flow. And yes i plan on getting coral.

 

[Harold Green]

There are some nice wave maker controllers including plug strips that can alternate pumps running. As a cheapie you can take two lamp timers that have 48 pins so you can turn a pump on or off every 30 minutes. It won't mimic wave action but it will change the flow patterns in your tank. Two timers with a pump in each, at opposite back corners of the tank can flow water in several directions, coming on and off opposite each other or overlapping each other by say 15 minutes.

 

[d2mini]

I tend to like using identical pumps across from each other.
But since you have two of the smaller ones, maybe you could do those two on one side and then the 425 on the opposite side.
As mentioned above, if you could get them to alternate that would be nice.
It's becoming more and more popular to have a gyre flow in the tank, so you could have the pumps on one end running constant for 30 minutes, an hour, whatever... then switch to the other side.