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I have a Koralia Nano and a Koralia 1. So far they are ok. I think my fishes like swimming against the current. They are super quiet also. I think I bought the older model Nano, but oh well. its still good.
I have a Marineland Penguin 550 for my 55g and it works great! It's really quiet and performs extremely well! In fact, I bought another one for my partial UGF system setup.
If you're wanting to use it as a mid-tank aerator, (instead of having the current skim the water surface), you can do that. That's how I have my powerhead setup in my tank and the fish love swimming in the current. I did modify it a little though. My Mollies are pregnant so I didn't want to lose any fry w/ the slits on the powerhead intake being so big. To remedy that, I just took the intake tube from my extra HOB filter and slid it over the powerhead intake grate. Works like a charm! I'm still waiting for my Mollies to give birth though.