White webbing-like substance in tank

[Delphinus]

Google vermetid snail and see if the nets they cast look like what you're seeing.

Unfortunately reasonably common in our reef tanks, they are a bit of a nuisance as the webbing both looks annoying and also will irritate corals.

[BCTugboat]

This does look like the vermetid snail webbing. Sand sticks to it as well. Maybe he's in one of the tubes on my mew featherdusters cluster of tubes. It was a LOT, more than I'd expect from a snail but I dont have experience with them. I'll be trying to get a picture up

[BCTugboat]

Heres a photo, had to shrink the size online.

[DKoKoMan]

vermetid snails will produce a web like in your photo. I know a couple reefers who are struggling to get them under control.