I really like this concept and your simple design. this is quite similar to some aquaponics systems that I've seen elsewhere. Keep us updated on how your prayer plant does. I'll be very curious to see since I have one myself. It's such an awesome looking plant I am determined to have it thrive.
Agree with the poster above about the soil. Using hydroculture media (ex. LECA, Hydroton) will be less messy and could probably even be better for your plants - given that you dose ferts separately.