When setting up a new aquarium, it is a good idea to make sure it is level. But you can’t accomplish this by taking just one quick measurement alone, and “eyeballing it” will never work. Instead, use a long level from your local hardware store and check to see if it is level from left to right as well as front to back. Don’t just check a couple sides of the tank, but make sure to check all sides, especially for acrylic aquariums as they can flex a little to make up for small gaps caused by stands that are not level. Once you have the tank level on the stand, you can start filling it up with water, but your duties don’t stop there. After the tank is full, check to see if it is still level, as there could have been a slight shift after filling the tank. If you do not level your aquarium, it could crack under the stresses caused by the pressure of the water.