Sponge filter lift tube question

Hello all,
I have a question about sponge filters. Does the lift tube need to be
completely under water or is it alright for the top of the tube to be
above water in air? This may sound like a stupid question but after
googleing I haven't found an answer yet. I just set up and started
cycling a 10 gal. tank for freshwater fish but I'm starting a 2.5 gal
tank to have a little fun growing those Triops shrimp.

IF the tube has to be completely underwater is it alright to cut the
lift tube down to fit?

Thanks for any help you can give!

Tom