Help identify the evil moss like problem

[whatsareef]

Currently in my sump... My problem, it is my guess that the culerpa has died off which is what I am seeing or am I wrong? ... or could this be some nuisance algae?

Thanks

[Richard]

Just looks like caulerpa with lots of hair algae growing on it to me. IME caulerpa tend to get covered with hair algae when allowed to grow out of control. Perhaps from dying caulerpa or maybe too much of the toxins released by caulerpa fuel hair algae growth. Best to trim back the caulerpa regularly.