just curious why the water in the aquarium tank would not leak out as shown in the picture provided below? The question is in the red circle. The water level in the aquarium tank is definitely higher than the hand entrance from what it seems. How they did that?

What sorcery is this?

enter image description here

  • 4
    $\begingroup$ The tank is sealed at the top. $\endgroup$ Oct 16, 2013 at 2:10
  • $\begingroup$ But still the water will leak out from the hand entrance there right? $\endgroup$ Oct 16, 2013 at 2:13
  • $\begingroup$ Atmospheric pressure presses down on the water floating outside the inlet (there's a reason it's shaped that way). If water were to flow out of the tank, it would leave behind a vacuum. Therefore, it doesn't leave the tank. $\endgroup$ Oct 16, 2013 at 2:21
  • $\begingroup$ Refer to this parlor trick for a similar effect: physicscentral.com/experiment/physicsathome/magicwaterglass.cfm $\endgroup$ Oct 16, 2013 at 2:24
  • $\begingroup$ @DmitryBrant Any maintenance job would require the staff to remove the top cover right? Or they could just seal the inlet first? Anyway thanks to your answer finally I get it. $\endgroup$ Oct 16, 2013 at 2:29

1 Answer 1


Probably, atmospheric pressure prevents the leak. If, as Dmitry Brant suggested, the tank is sealed at the top, atmospheric pressure acts from outside only.

  • $\begingroup$ Meaning if the cover is removed from the top of the tank. The water will flow out from the hand entrance there? $\endgroup$ Oct 16, 2013 at 2:21
  • $\begingroup$ Yes . It would help in draining fast, even if there is also a lower drain. (Usually during maintenance some water is left at the bottom so that the fish survive ) A container for water should be placed underneath of course $\endgroup$
    – anna v
    Oct 16, 2013 at 3:15

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