2. Your new fish needs to breathe! Bettas are in a category of fish called labrynth breathers, they get air from the surface of the water, so make sure there is room between the top of the water and the bottom of the tray for plenty of air for your fish, or he will drown.
3. You will need to keep the water clean! The plant's roots will die and leave toxins in the water, no matter how healthy your plant is. Those toxins are very bad for your fish, so to keep your fish and your plant healthy, make sure to change the water every week and trim the roots when any start to look unhealthy.