When I first saw this public aquarium in Oita, Marine Park Japan, I couldn't think how the vacuum would prevent the water coming out.Then I thought of those "bird drinking dispensers".The clear plastic tube, sealed at the top with a small bowl at the bottom.When the bird drinks from the bowl, the water level drops allowing air to enter the tube until the the water covers the entry point again.
The "test rig" shown was to see if these open hatches would "hold" on a tunnel.As you can see, they don't!But fortunately the lower tank is big enough to catch the water from the tunnel.
On careful study of the Japanese aquarium, you will see that the open hatches are on a line with the water level in the lower aquarium.
On my test, when I pull the rubber stopper out, the vacuum immediately pulls the small amount of water covering the hole, followed by air, thus displacing the water in the tunnel.
Now I sincerely hope that doesn't mean my "special area of knowledge" is "the bleeding-obvious"!
Since seeing this idea many moons ago in that article by "Bio-Elite" on the plastic tube linking 2 aquariums, I have spent a lot of time researching this idea.The first record of this principal is described in a U.S.patent issued in 1934 for linking 2 aquariums by plexiglass tube filled in a bath tub and placed open ends down on 2 aquariums.
In 2003, a U,S, patent was filed for and obtained in October 2005 for an aquarium enhancement system using a vacuum.Nothing built and tested, but very detailed drawings showing the ideas and concepts.Close to the "Romaurie Effect" but without the small details like how to make the connections to the aquarium for providing both a vacuum and fresh air inlet.The sort of detail that only comes from thorough research and development.
I only learnt about this US patent recently.And only after exhaustive research on the internet.My system was up and running 1 year before this patent was issued.But 2004 was a "special" year for this concept."Google" "The Fish Highway" for a book published [now out of print] on how to build an aquarium tunnel.The "Liquid Potion Coffee shop" Ohio with what must be the longest tunnel yet to link 2 aquariums.
Very small acrylic aquariums with a tunnel attached, now available with a plastic tube to suck the air out.
"Never a dull moment"!
It reminds me of a David Frost interview with the heads of a Japanese bearing manufacturer many, many moons ago.Somehow he got these guys cornered on his show and displayed the original British made bearings and packaging alongside their product,It was a direct copy.None of them would comment!
Now this marine park won't even acknowledge that they have the largest "vacuum-enhanced" aquarium in the world.
Can't really complain.They have this ability to take a western concept working on "plus or minus" half inch tolerances and "blue print" it to a fraction of a millimetre.Just look at the Triumph Bonneville 650cc twin along side the Yamaha 650cc twin.