i just fired up my 20 gallon wet dry sump setup. it is for a all glass 90 gallon with built in overflow. i am using the all glass pipe kit as well. it is making a gurgling sound it seems every 15 seconds or so. my drain hose is looped because it was too log but i was told that should not be the problem. i have heard making the air flow hole in the top would help. any insight on this problem is helpful, thanks.