Overflow box placement

[bkvreef]

I presently have a 110 with two overflow boxes.
However, I have a 210 that I will be setting it up shortly. I need to know should I buy 1 large overflow and put it in the center, OR should I get two and put them in opposite ends of the tank (like I have now.)?
My present tank is 6' x 18" x 18". My new tank is 7' x 2' x 2'

 

[prime311]

You can do either really. 1 overflow will give you less of an imprint in your tank. 2 overflows will give you better surface skimming. Its your choice.

 

[mkzimms]

Originally Posted by prime311
http:///forum/post/2622730
You can do either really. 1 overflow will give you less of an imprint in your tank. 2 overflows will give you better surface skimming. Its your choice.
not necessarily... surface skimming is about the linear overflow.
one overflow box that is 12" long has the same linear overflow as two boxes that are 6" long. so two boxes will not always give you better surface skimming than one box.
i think where you should place the boxes is more determined by how your return system will be setup to maximize your flow all around the tank... ie: a return on the right side of the tank and the overflow on the left side will cause all the water to move across the tank, or a return in the middle and overflow boxes in each corner will create two counter rotating currents.

 

[prime311]

Well just from what I've seen the dual overflows aren't much bigger then the single so dual will most likely provide better skimming, but you're right it is dependant on the size of the overflow box in the DT.