We did put the guard on as a precaution and we don't even have any fish or cleaning crews at the moment! haha....
Inside our booklet for the Koralia, you can order just the prop as a replacement part. Each Koralia model has a separate part number for the prop, but if you would like the number, let me know which Koralia you have and I can send you the part number.
So far we can see a big difference in the water flow. We are thinking about getting one more for the other side of the tank. We are just starting out and only have sand, water, and salt in the tank. Right now, it is that cloudy mess we have read about. lol