Encryption and replacing hard drives in a MacBook Pro

I have a mid-2009 MacBook Pro and decided to change out the hard drive for a solid-state drive. The existing drive was encrypted using FileVault. I put the solid-state drive in the external enclosure and use superduper to make an exact copy of the internal drive. I replaced the internal drive with the solid-state drive after it was copied and everything worked fine however I was no longer able to use FileVault to encrypt the solid-state drive. I was aware that using an external hard drive required the drive to be formatted with encryption but since I was putting it back into the computer I assume that FileVault would encrypt the drive just as it had when I encrypted the original internal hard drive. My question now is there a simple way to encrypt the new internal hard drive? Also, is there any particular problem running the new internal hard drive having made a duplicate with superduper from the former encrypted internal hard drive? I neglected to mention that I'm running the latest version of Lyon.

thanks for looking this over,

Scott