As long as there is now gap for air to get in (IE between the gravel vacuum and tube) there should really be no problem. Unless of course the output side is above the input side.
I would try using just the tube, and make sure to keep the output side below the input (that is submerged in water)
As far as pumps any power head for aquaria should work fine but they aren't designed to run dry, there are small water pumps but they may cost more.
I myself always did the whole suck on the end trick, just be careful not to get any in your mouth it tastes bad. LOL
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Jeremy
"I am become death, the destroyer of worlds" July 16, 1945 Robert Oppenheimer
1.1 Double Het "Sharp" Snow RTB's
1.1 Hypomelenistic RTB's
0.2 Pastel Hypo RTB's
2.0 Double Het Stripe Albino RTB's
0.1 Suriname RTB
0.1 Anerthrystic RTB
0.0.11 Red Bearded Dragons
1.1 Rhinoceros Iguana's
1.0 Green Iguana
1.0 Ball Python
1.1 Cream Golden Retrieviers
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