True on the first statement. They work quite well.its not a protien skimmer, its a surface skimmer. it skims things off the surface.
Ive never actually used one personally, but I know that sometimes they can be loud, with the sound of rushing and gurgling water.
True on the second statment only if you don't use the integral flow adjustment valve on the Hagen and Fluval brand skimmers.
v/r, N-A