A German YouTube user, “TCHelmut,” designed an interesting addition to his garden pond to give his Koi fish a view of the world. By turning the design of a standard fish tank upside-down and installing it in the middle of the pond, he created an observation tower where fish can come and go freely.
The tank doesn’t have a bottom, leading to its “bottomless aquarium” nickname, although people also call it an “anti-gravity aquarium” because of how the water in the tower seems to defy gravity.
The fish swim around the tank and stay for as long as they want, with some even spending hours there. On a normal day, about 20 fish spend time in the tower. They’re able to swim all the way to the lid of the tank. The tank gives the fish the opportunity to relax in the sun and see the world from a different perspective that most fish never get a chance to experience.
The creator built the structure by hand and filled it with water. He uploaded a video of the tank to YouTube in 2011. The tank is made of glass and all the walls are 1 centimeter thick. While fish tanks are usually horizontal, this tank’s vertical design allows it to stand in the center of the pond.