What makes the tunnel???

[Almondsaz]

Can anyone advise what invert makes the tunnels in the sandbed that you can see on the glass. It looks as if all the detritus(sp) is inside the tunnels and it appears to be a very small bug like creature. There are lots of them against the glass that I can see.

But does anyone know what they are and their purpose?

 

[Amphiprion]

Probably just gammaridean amphipods. It isn't uncommon for them to make little burrows out of mucus and whatever else is around, which includes algae, detritus, etc.