nope wont hurt the power-head you just might loose a tiny bit of flow
if I remember corectly someone even makes sponge material to go around a korilia power-head
but if you cant find it
I use this if I ever have to protect somthing like that
http://www.lowes.com/pd_78359-1410-F...937087_?rpp=60
or similar sponge material like that
with your korilia just wrap it around the outside and use 2 or 3 or more if needed rubber bands to hold it on the pump