power head help me

[Kiel'thalin]

A majority of reefkeepers will agree with multiple powerheads usually placed on opposite ends of the tank. This is not the way to go on a 55g. On a 55g being only 12.5" in width, a single will do it if it has enough power to reach across the entire tank and most likey will have enough momentum. If you place a powerhead on each end of the tank they will be facing each other because of the width. In that configuration you WILL have dead spots since they are working against each other. On wider tanks you can place one flowing down the back and one flowing on the front, but not aimed at each other. A majority of people load there tanks up with powerheads usually in a quest to get rid of dead spots. If you have enough flow from a single source you can cover the entire tank no matter the size. Here is an example my old setup that utilized this method...
Click for Example

 

[Sploke]

You are corect in that this method of laminar flow can be used in some applications. However, I tried it in my 55, and it did not work. I have a 4" sand bed and lots of soft corals and zoas. Regardless of where I pointed the power head in order to get a good gyre flow going, it ended up blasting the heck out of a soft coral, or blowing the sand bed all over the place. With SPS and no sand bed (as your tank pictured is, mostly SPS anyway) this is a little easier to avoid. To get good flow in my tank without disrupting everything, I need multiple sources of lower flow rather than one single high-flow source.

 

[Amphiprion]

A majority of reefkeepers will agree with multiple powerheads usually placed on opposite ends of the tank. This is not the way to go on a 55g. On a 55g being only 12.5" in width, a single will do it if it has enough power to reach across the entire tank and most likey will have enough momentum. If you place a powerhead on each end of the tank they will be facing each other because of the width. In that configuration you WILL have dead spots since they are working against each other. On wider tanks you can place one flowing down the back and one flowing on the front, but not aimed at each other. A majority of people load there tanks up with powerheads usually in a quest to get rid of dead spots. If you have enough flow from a single source you can cover the entire tank no matter the size. Here is an example my old setup that utilized this method...
Click for Example

Multiple powerheads only don't work when placed improperly. I can assure you the issues you find with using them on a 55g tank can be circumvented with, as you said, careful placement. It will just take some experimentation.