Weird algae in my fuge

[Canadian Man]

So I have this weird algae in my fuge. It grows so quickly that it covers everything! My calurpa, rock and other critters in my regugium are burried below the stuff. It's basically in my fuge only.

It's like a sponge and grows in big mounds. When you pull it out and squish it it seems like it's holding water. It's brown in color and when I pull it all out it only takes about a week and it's all back.

I don't have a picture as I am not at home now.

I mesured my nitrates and they are at 0 as well as my phosphates.

Any ideas.

I guess that's what a fuge is for but I would much rather see calurpa and sargassum like I had growing before.