Strange blob on glass?

[a.t.t.r]

I know this is a bad picture but there is this strange blob on my side glass with a single long “tentacle” of what looks to be slime. I can not figure out what it is any clues? About the size between a penny and a nickel I’d say

 

[KyleNachoFriend]

Hard to see, but could be a pineapple sponge?

 

[a.t.t.r]

Hard to see, but could be a pineapple sponge?

No. It’s brown and definitely gelatinous. It’s also in a spot I can’t get to from inside the tank without moving rocks.

 

[Goaway]

A flatworm maybe

 

[a.t.t.r]

A flatworm maybe

Maybe but that would be one large flatworm. Never seen one that big