Plants suck out nutrients (nitrate, etc.) in the water. As the nutrients are obsorbed the plants grow. When the plants get unhappy for some reason, like not enough light, not to much to eat, etc. they turn white and release the nutrients back into the water. I am talking about caulerpa. The Cheatomorpha doesn't do this. Also Razor has some cool plants that suck out the stuff and look good at the same time. I like your plants Razor, they look clean for plants. Red mangroves are good too. IMO.