Any marine grass, be it turtle grass, or sea grass isn't the best macroalgae to start out with. Not only do they need higher lighting but very deep sand beds around 6 inches deep or close to that amount. They also need to be established and have they're root systems take hold.
Macro helps out with water quality if you have a lot of it. I have about a pound ( those little plastic fish bags FILLED with it when i recieved it) in my 10 gallon and the water stays crystal clear constantly. Caulerpa and cheatomorphae and some of the best types to start out with.
I'm tired of getting pointless messages. If your going to start a conversation or ask me something, keep up with it.