Power heads

Hi everyone, I am confused when it comes to power heads for my 125 tank
One person at a fish store told me that I should have the power head aimed up towards the top of the tank creating a wave in the water which will vent the carbon monoxide and create oxygen
Another fish store told me does not matter, better to aim down as aiming up will cause you to have to add water more often
Well I tried both ways and it seems like having one up does make a difference as when I don't have one aiming up my fish seem to breath hard and act like there dying
so I have one aiming up and one down towards the center of the tank aiming straight across
The fish seem to like the power head that's in the tank, in fact I see them all acting like a bunch of kids fighting over it, they love staying in the current, looks like there on a tread mill,
I think the power head I bought for the lower part of the tank my be a bit to strong ,could not find the size I wanted, seemed like the ones they had in stock were either to big or to small so I went with the big one that cycles 900 gal per hour ,have to tell you its pretty strong, in fact it will reach three quarters of the way to the other side of the tank, the tank is seven ft long
Is that to strong?????????????????, the fish seem to love it, thank goodness they don't go right up to it

[Clown Monarch]

My 2 clowns love the current too. They'll start at one end and swim against the current until they are maybe 2 feet from the PH. Then they'll stop swimming and let the current carry them to the other side where they'll do it again.

That's what mine do also, I guess they know better then to go right up to it

Is there a rule of thumb in ref to what size power head to use?

[Clown Monarch]

All I know is that some here suggest having flow 10x the size of your tank (for a reef tank). My tank with 4 PHs supposedly turn the water over almost 12 times per hour. I may cut this back depending on whether my corals like it or not.

Well I have the 900 running below and a 400 running up top to create a wave affect on the top of the water so that's like 1300 gal per hour, I have another power head but I figured that's enough

[Clown Monarch]

It seems that some go overboard on flow and light.

[Atari]

It's just a rough guide. Everyone's tank will be differently aquascaped so their flow requirements will vary also.

I had 20x when I started and it still didn't seem like enough, but I didn't want to add yet another powerhead, so I changed the aquascaping and suddenly anything over 15x was too much.