Unidentified spiderweb lookalike algae ?

[Heelllooo]

Could someone help me identify those weird threads that grow in my tank ?

It's been two days that they are there in my tank when the light starts.

They look like spider web but more dirty ( like dust/detritus on them ) and more dark grey. They are very easy to remove and they broke into piece when I touch them.
I have some staghorn algae in the tank right now and they seem to like to attach themselves to it.
I'm not even sure it's algae.

 

[Simon Cole]

There are a few aquatic spiders that build webs underwater, including the diving bell spider <Argyroneta aquatica>. They can give a nasty bite.

Filamentous bacteria can also form web like structures; I have seen this before in medical treatment tanks where the microbial balance shifts to allow them to fully colonise.

 

[_Maq_]

Filamentous bacteria

... and what about fungi? Is that possible?

 

[Simon Cole]

... and what about fungi? Is that possible?

Good question. I don't know. Aquatic fungi are often referred to as a "neglected class" that are simply "forgotten".
Mariyana Vatova (a key researcher in this field) is quoted as stating: "...many groups of aquatic fungi are poorly studied, and many species are yet to be discovered and described." <reference>

 

[_Maq_]

Aquatic fungi are often referred to as a "neglected class" that are simply "forgotten".

And yet, if I'm not mistaken, fungi are crucial for decomposition of matter rich is polysaccharides and poor in nutrients (wood, leaves, ...).

 

[Heelllooo]

Ok so weirdly today I don't see anymore of it in the tank. It disappeared as fast as it came. But I don't want to talk to fast.

I looked more at it yesterday and it definitely didn't looked like algae, I would clearly lean toward it being bacteria or fungus.