i have not seen this mod on any forum anywhere and i have looked quite a bit so i figured i would let you all know about it. i had some koralia 4s and a koralia 2 and i got to thinking if i could get more flow out of my k2 cheaply. i switched an impeller assembly from my k4 to my k2 and vualla k4 flow out of a k2. i liked this because the body of it is smaller and if you happen to have a lower flow koralia sitting around you can order a new impeller for under $10 at many online stores. i have not tested it with any other models other than a k4 and k2 but i would imagine 1-4 all impellers would be interchangeable since the magnets are all the same size its just the impeller shape and size its self that is different, and the body of the powerhead is larger or smaller but the larger impeller does fit in the smaller body and work. just a nifty trick i happened to figure out randomly when i was bored one day
happy reefing