Advice needed on fluid dynamics

[Anonymous]

Or "Where should I place my powerheads?"

It might seem a bit late to be asking this question 9 months after setting up my tank, but I'm nothing if not pigheaded and stuck with my current arrangement long after it became apparent that it wasn't doing what I wanted. My powerheads (two Tunze Nanostream 6055s) are currently placed on the back glass of the tank, towards the upper left and upper right hand corners. See picture below (click twice for a full size version).

[rimg]http://i867.photobucket.com/albums/ab238/TheEscapedApe/Long%20awaited/P1010084.jpg[/rimg]

The thinking was that I'd then have the stream of water from each hitting in the middle of the tank, creating a nice area of turbulent flow in the central area, where I'd be most likely to place my SPS, should I ever buy them.

However, what has in actual fact transpired, is that the flow from both streams hits the front glass, creating downward force and blowing the sand at the front towards the right and left and back towards the center from the bottom. So I have sand piling up there and a big hollow at the front. Plus fine sand continues to blow up and land on coral. After some stability had been achieved, this problem was exacerbated by the earthquake, which shook and loosened up the sand bed (turning it into a milk shake soon after, though it settled again quickly).

What I would love to achieve is a turbulent, high flow area in the center of the tank, but with areas of relatively lower flow around the sides of the tank.

My question is in two parts:

1) is it worth playing with the powerhead placement now? Or should I again display patience and accept the odd sandscape?

2) if I were to move the powerheads now, what would be the best positioning to achieve the effect described above?

Any advice much appreciated.

 

[Anonymous]

I would move them. Try one in the back right corner, the other in the front left, both pointing along the long wall. This will get you a gyre and get the entire mass of water moving.

 

[Anonymous]

I would move them. Try one in the back right corner, the other in the front left, both pointing along the long wall. This will get you a gyre and get the entire mass of water moving.

Thanks for the input Rich. So the one on the front left would kind of point diagonally back towards the back wall? Or along the front pane of glass?

Bearing in mind that I'd like to have lower flow around the edges (as that's where the lower light corals are, which tend also to like lower flow), wouldn't that create more flow round the edges? Or am I missing something?

 

[Anonymous]

I would keep the one on the top left and move the one on the right closer to the bottom and point it at an upward angle to the left and toward the surface.

 

[Anonymous]

I would move them around till you get a flow you like.

 

[Anonymous]

Thanks both. I'll start fiddling and see what works best.

 

[Anonymous]

I would move them around till you get a flow you like.

This is a good suggestion.

If it were me I would put one on the back wall of the tank near the corner and aim at the opposing front corner and adjust as necessary. Make a X with the flow.