This is an interesting way to turn a classic science experiment into a functioning addition to a fish tank. It makes a pretty cool display!
Be sure if you try this to have plenty of water circulation in your tank or the water in the suspended area could become oxygen deprived. There really shouldn’t be any problems if the tank is well functioning prior to adding the new compartment. You may also want to put a wide base of some kind below the supports so the extra weight is spread over a larger area and you won’t risk cracking the bottom of your tank.
I learned the trick with the styrofoam float from this video: https://youtu.be/miAfNiVWjqw