yeah...100% serious...I was skeptical but after these past two weeks...forget the expensive light for chaeto! I bought 5$ worth from the LFS and now i've got a piece about 12 inch square....started off the size of two brillo pads...now its huge. Once my nitrates are under control, i'll trade it to others. My wife is even amazed....i originally was trying to keep it in the display tank but the light was only on for 10-12 hours....didn't grow much at all over 2 weeks....give it a try, with this hobby, its a small investment!