hmm.. there is no tube running to the outside as far as i know. It came with horrible directions too. I do leave it running full time, it does have what you explained (the collection cup where it should come up the tube and spill into the cup) but a gain it hasnt done that yet. the tank has been up and running since the 2ncd of this month, so were at almost 4wks. There is what looks like brown staining inside the tube the yuckiness would come up through but no real waste has collected at all. The collection cup is pressed all the way into the unit.
http://www.aquarium-supply.biz/Photo...tCode=RTI01014
thats the one we have.. i know your not supposed to post competitors but its the only way i can share what it is.We do have two of them but were told it wasnt ness.
For aquariums up to 20 gallons
Simple installation and compact design
Adjustable variable venturi with exclusive air/water mixing chamber
Filter cartridge with activated carbon
Ozone compatible
110 gallons per hour pump included
Dimensions: 7.25"L X 4.5"W X 10.25"H
Will only fit on tanks with a lip of 3/4" or less