Questions regarding Hydor circulation unit

[indigo1975]

I put this Hydor circulation unit in my tank..
It's only 425gph Wich is good my last overpowered
One was pushing crap all around the tank..

Question. My brother told me to place it up high
To circulate the water on top so crap does not
Form on the water.. I wanted it a bit lower
Because when I have it this high I makes
My plants lean to the left.. Does it have to be up high
Where is best placement

 

[indigo1975]

think its a circulation thin a ma bob.... its a small one