"Touch Tank"

In an otherwise average aquarium, this feature really stood out. You can put your hands through these moon pool-like holes and touch the fish. Has this been done anywhere else?

September 2015.

Was this tank designed by M C Escher? I can't see why the pressure of the water above the hand holes doesn't force the water to syphon out through them. Are they sealed in some way?
BTW I hate the breeding and display of those poor misshapen hybrids known as 'parrot cichlids'.

Alan

Hi Gentle Lemur. I’m not sure how it worked, but the holes definitely weren’t sealed. I’ve uploaded this photo to prove it:

http://www.zoochat.com/657/amp-quot-touch-tank-amp-quot-435242/

I was so confused when I saw this, but that kind of makes sense. It doesn't affect the fish in any way presumably?

Thank you Chlidonias - that does solve the mystery.
I did some rough calculations - if there is 50 cm depth of water above the openings, the pressure of the air above the tank surface has to be reduced by about 5000 Pa, or 5% of atmospheric pressure, to prevent leakage: that would not be difficult to achieve with a decent air pump. Damned ingenious
They must have specially shaped plugs to block the holes when they turn the air pump off and open the top of the tank for cleaning and maintenance.

Alan

BTW: the Assistant Curator should not have used the word 'vacuum'. My old Physics teachers would have chewed him out for doing so. At least he didn't use the dread phrase 'partial vacuum'. The air pump simply reduces the pressure of the air on the surface of the water inside the aquarium.