This size is WAY to small for a betta! A betta needs at the minimum of 2.5 gal and does best in 5 gallons +. Also, betta JUMP! Without a cover for the opening at the top, you will find your betta on the floor quickly. You will need to do a water exchange on this tank every two days, or the poor water quality will harm your fishie friend.
DO NOT follow these instructions on cleaning! When you clean you CANNOT USE SOAP! You will kill your fish! No matter how well you rinse, there will always be a residue of soap left on the walls.
I have kept betta fish for over 5 years and breed them. Please follow my advice!
I do see how this could be used for other living things, such as plants. It could be a neat project for children watching root systems grow.