Looks like rhizoclonium to me. Overdosing excel OR a dose of AlgaeFix will clear it up. If you go the AlgaeFix route make sure you don't have any inverts in the tank because that stuff will kill them.
You really need to find the imbalance in your tank that is allowing the algae to grow. What lighting are you using and how long is it on? Are you dosing anything? What is your feeding schedule and how much? What are your PH, ammonia, nitrite, and nitrate levels? Are you doing weekly water changes and how much water are you changing?