I have an ETSS 800 dual downdraft skimmer. I 've got it hooked up to a pan world 200 pressure pump. It is in sump with the water just covering the bottom black chamber. I can not get this skimmer to skim wet, I can get lots of mud to collect in and around the collection cup neck but hardly any wet skimmate. Does anyone else with this skimmer have the same problem? And if so what have you done about it?