The rattling when starting up is said to decrease the overall lifespan of the pump. Some people have used the seio controllers which rev the power up and down (without stopping). Keep in mind that if you use the controller, it voids the warranty of the controller and the koralia. I've heard rumors that Koralia will come out with a controller of it's own, but haven't seen anything definite yet.
If you don't need a wavemaker, the Koralias are an excellent choice. I have a mod maxijet too and it puts out more flow, but not as wide as my Koralia 4's. I like them both, and get good random flow with them bouncing off each other and the glass.
Fair warning, I hooked my 2 Koralia 3's up to my Wavemaster Pro to see what would happen. I know the clicking on startup comes from the impeller being pushed forward before it settles back into place, so I placed a very small piece of airline tubing there to stop that (thanks Fat Tony ). They were silent at startup so I thought I had it licked. The problem is that when the Wavemaster kicks on it has various timings and sometimes doesn't stay on long at all. What I found is that while most of the time the pumps would push the water out the way they are supposed to, every once in a while they would start in reverse and actually be pulling water into them instead. I am glad I didn't just say everything is good and walk away and leave them running like that.
I now have a Red Sea Wavemaster Pro for sale that is in excellent condition, all of the outlets and the lights work, if anyone is interested.
Wolf, the propeller "kicks" at start up in order to seat itself properly and have the impeller rotate so that water is pushed out. I've heard it explained, it has something to do with alternating current. By placing the airline tubing there, you're keeping it from seating itself properly. If you remove the tubing, it will work like normal again.
they don't work with a wavemaker. They say specifically not to use them with a wavemaker, iirc. we see them broken all the time at MD because they were set up with wavemaker. I definitely wouldn't recommend it.