My project:
You'll need a clay pot with a opening dimension of about 5 1/4", a cool whip container (the larger size works best), marbles, and a dremel or tool to cut a hole in the pot.
Synodontis petricola are scatter spawners, which basically means they let their eggs drop wherever they spawn. As a result, the eggs and babies have a tendency to get eaten by the other tank inhabitants. Using this cave, you can drastically improve your odds of spawning petricola.
Take a clay pot and cut a hole in it using a dremel or perhaps a hole saw if you can find one that can be used to cut through ceramic or clay. If you cut a hole about 1 1/2" in diameter, it tends to encourage them to use the cave.
Add a layer of marbles about 3 deep in the bottom of the cool whip container, and place the pot on top of the cool whip container.
What the marbles in the cave do is allow a place the fish to spawn, and the eggs drop between the marbles where the fish can't get to them. If you check the pot about every 5 days, you'll eventually see eggs in the bottom of the container. You will have to remove the marbles by hand in order to see them, as they are very small.
This method can also be used with other scatter spawning fish like danios. In that instance, you would just have an open container (like a rectangular tupperware container) filled with marbles on the bottom of the tank.
