hi
i have that happen in my refuigm alot when the cupltra reach the top.what i do is trim off 1-3 inches (provided the alga is rooted to the side) and i cut off the brown tip and i stick the inch or two back in the refuigm to regrow i harvest once a month so that is when i trim mine down.But the brown tips on mine are from the light being to close to the water.