this toy creates a slow, but steady foam that just keeps going.

Step 1: Materials

aquarium air pump - mine has a check valve. handy for bathtub use.
plastic tubing - I used 1/4 inch, but its not critical, it just has to fit the aquarium pump.
sponge
two nesting containers - I used yogurt tubs
two cable ties

Step 2: Sponge Preparation

Trim the sponge to fit in the bottom o the outer container.

Then stab a hole for your tubing

Step 3: Container Preparation

Cut a hole in the bottom of the inner container just smaller than the sponge.

Next cut a hole small enough for your tubing to fit through.

Step 4: Bubbler Assembly

Thread the tubing into the small hole, and insert it into the hole in the sponge.
Then shove the sponge into the larger hole.

Step 5: Final Assembly

Stick the inner Container into the outer one. You may want to test the bubbler now. I used a squirt of dish soap and a few inches of water.

Once you are happy with the results, you can poke some holes near the top and zip tie everything together. Make sure to secure the tubing with one of the ties.

We used it outside and in the kitchen with dish soap, and in the bathtub with bubble bath.