What is this on my tank wall?

[Tambe]

Can anyone tell me what this is on my tank wall?  It’s maybe the circumference of a dime.

[Ken Burke]

Snail eggs*?

[H.K.Luterman]

Those are snail eggs of some sort. Ramshorns, pond snails and bladder snails all lay similar egg clusters. 

[lefty o]

alien life form. snail eggs is the likely winner.

[Guppysnail]

Snail eggs definitely. My bladder snails when they lay on glass/hard scape the gel sac is usually kidney bean shaped and lacks the individual chambering around each egg that this one has. Hope that helps. Welcome to the forum  

Bladder snail eggs on plant. 

Edited February 22, 2022 by Guppysnail

[Torrey]

So far, in my tanks:

Pond snails lay a very firm (firmer than silicone) linear egg sack, where the egg deposits look like parallel rows, with the actual eggs alternating in the two rows.

Bladder snails lay in a distinctive kidney shape, as Guppysnail showed.

Ramshorns deposit perfect circles of egg sacks.

I'll try to find eggs in the tanks, the endlers tend to eat them before I can find them. 🤷‍♂️ So unless I am lucky enough to have the camera *when* I see one of the snails laying, I don't have much of a chance getting the picture😁