IMHO,there is no such thing as over skimming. There is choosing the wrong skimmer and not havering as large a bio load as you think you have. Many reefers choose by brand or reviews which is good as long you understand not just your present needs but your future needs. When I choose a skimmer I am concerned with the pump size ,air volume and chamber diameter which in turn adds up to contact time which is what counts. My bubble king pulls twice the water and air as my diablo,which is why it out performs it hands down. Both skimmers pull good amounts of skim one just does it way better. The BK has a much larger neck also. We house 22 fish so good skimming is a must. If you are pulling good skim and everything looks happy join em! Regardless of your neck size !? Lol.