Koralia's are great. For my 10 gallon, i got a 240 nano, but that was too much flow, more suited for a 20 gallon or so. I ended up getting a rio 50. Smallest they had and it came with a ball valve to adjust flow. It still provides too much flow but thankfully i could adjust it.
One thing I would like to note. Rio although its more of an eyesore to look at, i like it more for the attachments, the flat nozzle does a great job spreading flow and i point it up to agitate the surface. Also if you got shrimp, juvies will get sucked into the koralia, on the rio, I actually put filter floss and tied it down to block the intake vents and the shrimp cant get sucked all the way in.