It's just not going to happen with any amount of plants raysdig in substrate and they will dig them up fast no matter how many you have
Discus may work when the rays are small but don't under estimate the power of a large ray you discus are living on borrowed time
Not many mid water fish are safe with a ray 10 inch +
As for keeping them well fed large rays kill for fun not always for food my rays just killed a 12 inch tinfoil barb for fun they always do it when the lights are out
T1 is right. they migh work for a short time but eventually everything in that tank has a good possibility of disapearing. as far as reburying everything as well would be a hassle on the plants