Does the hose have to perfectly straight up and down to work? Can they be crossed somewhat? The back of my aquarium stand gas a wall with a hole drilled in it so I have to make it kind of curved to be able to make it reach the top of the aquarium.
Should be fine, I had mine crossed until I figured out how to completely make it straight and it still worked great.
How do you know if the filter is working properly? Does the out take part go below the water?
It can go above or below the water, doesn't matter. I keep mine underwater, but if you want alot of surface agitation you can put it above. The filter was working properly because even though I made it straighter, flow barely changed anyway.