also since it doesn’t attentuate there’s no resulting low pressure…

water is an amazingly unique and interesting material in terms of physics… which is partially why it has it’s own dividion of the subject (hydrophysics)

What is a Fish Highway?
Imagine a means for fish to swim out the top of your aquarium, up to the ceiling, across the room and then down into another tank. That’s a fish highway. Click here to see an illustration submitted in 1877 for the first one patented in the US. Today they’re made of acrylic plastic, the same material used for many custom built aquariums.

Why doesn’t the water spill out of the highway?
The highway tube is completely sealed except for the openings at each end which are submerged below the tank water levels. Like a large drinking straw, when the air is sucked out of the tube the water rises inside it and will stay there unless you let the air back in.

Do the fish swim in it?
Do the fish swim in it.

Does it harm the fish?
As the fish swim higher the pressure drops a little but it’s only slightly lower than the pressure pressure in the tank.

How do you fill it?
When the air is sucked out of the sealed tube the water from the tanks flows into it. Eventually, after all the air is removed the tube is filled with water.

How do you clean it?
Water flows through the highway continuously so the tank filters clean the water in the highway. Algea is removed using cleaning magnets for acrylic tanks.

How does water flow through the highway?
Water is pumped through a separate pipe from one tank to the other using a small pump. As the tank water levels change (one rises and the other falls) flow is induced through the highway by the force of gravity.