What size powerhead?

[speakerfish]

I read the post below about placement of powerheads, I think I understand that but what size should I get? I have a 20g long with the clip on filter located aprox in the middle. I was thinking of getting a 170, I figured that would ge a good size. Will one be enough or should I get two and place them at oposite corners of the tank to create cross currents?

 

[cap'n pete]

170 GPH? Are they adjustable flow rate? I would go with two in the corners, versus one with a higher flow rate.

 

[speakerfish]

I think 170 gph is what it said, seemed high to me so I didn't buy it. I'm not sure if they are adjustable or not, I don't have any knowledge of powerheads. I'll just pick up two smaller units, should I wait until after my tanks cycles or install them now? Thanks for your input.

 

[slick]

I would install them now and also you can go higher on the gph. Just think about how much current is in the ocean.