White web growing in sand bed

[Kalipanther]

What is this white spider web looking stuff growing inside my sand bed. I first saw it growing in a corner of my 125g. It looked like an ant farm kind of, like tunnels in the sand. Cleaned sand bed and it went away. 3 months later, it pops up when I put in a shaving brush plant. I moved it to my refugium, and it grew back.

 

[Miklo_Miklo12]

do you have any fish in there ?

 

[P-Dub]

Sponge or microbe of some sort, my best guess. Hard to tell with the photo provided though.

 

[Kalipanther]

do you have any fish in there ?

No, this is one of my refugiums.

 

[Kalipanther]

Turned out to be the plant dying. Mold? In case it helps anyone. Then 6 months later I am seeing small white sponges growing in the shadows of refugium. I remove them with a chop stick and set up filter floss to catch them. Thank you all for responses