Glass bottles in your tank..?

[Circus]

Ah I could fill the bottle with sand to match the level of the tank.

You could try a different colored sand, to make it contrast maybe? A red or black? Now I want to do this with a tank, lol.

 

[Fishfaced]

You could try a different colored sand, to make it contrast maybe? A red or black? Now I want to do this with a tank, lol.

That could look cool, like your thinking.

 

[Fishfaced]

I've been trying to think of a safe material I could use that would look like a scroll of paper.
I could pop that in then cork the top.

Message in a bottle.