I'm very interested in experimenting and giving this method a try. How air-tight does the tank need to be to maintain sufficient moisture? I don't have a glass lid. Should I wrap the tank up with plastic wrappers and make 100% air-tight ?
There needs to be some air circulation, but the main thing is that the plants don't dry out completely. The substrate needs to be very moist. I'm growing HC emersed in a little 3 gallon and all I do is mist the plants really well every day and add a little water when the substrate gets dry. It's not covered and things seem to be coming along well, but its probably best to at least have a galss canopy on.
What size tank are you planning to grow it in?
What lighting?
What substrate?
Hope that helps a little. I'm sure someone else with a little more experience will chime in.