Homebrew PCBs

I picked up a fish tank pump and a container that should be good for 
my first etching tank.  When I picked up the fish tank pump, I also 
noticed they had these thing that looked like porous stone that are 
used to spread out the bubbles.  I bought one, but dropped it on the 
floor before I had a chance to see if it worked.

So, I am wondering if there is a good way to get bubbles to spread out 
across the bottom of my container?

The fish tank thing only cost $1.00 or so, so I really don't mind 
buying another one to try, but I figure some of you creative folks 
here might have better method.

Chris