I have this skimmer http://www.marinedepot.com/a_ps_va.asp?CartId= At the top there is a little pump in upper right hand corner of the skimmer with an adjustable carb either open or close. I am wondering what this does exactly and also if it should be open or closed.. I have a 55 gallon Tank with 2 clowns, 3 damsels, a fuzzy dwarf, and a foxface.. When i first purchased everything my local fish guy told me to cylce the tank with the carb closed now that it has cycled and there are new fish in it im not sure if it should be closed or set to open.. I cant get a hold of him lately either.. Can anyone help me out here?