Hi, Will!
I'm trying to grow them. The first batch I got from Floridapets.com didn't do so well, I think it was because my DSB wasn't "ripe" yet, and it shipped in the hottest week of the summer, UPS drove it around all day, etc. This batch looks really strong, and the sand bed is really rich, so I'll keep you posted on how it does!
I have three types, Thalassia, or "turtlegrass", Shoal grass and Manatee grass. (don't know latin name on those two).
Do you think if the Manatee grass really grows it'll attract a manatee to my tank? I keep lots of bamboo, but no pandas have shon up yet. ;(