Final answer:
The initial step in setting up an aquatic chamber is to set up two connected water containers, one for fish and the other for frogs, to study frog egg laying in reaction to the presence of fish.
Step-by-step explanation:
The first thing to do when assembling an aquatic chamber is to arrange containers of water in such a way that water can be freely shared between two compartments.
This is essential for conducting experiments to observe and compare the egg laying behavior of female frogs in the presence and absence of predator fish in the fish tank. One compartment would contain fish, and the other would contain frogs. Depending on the experiment's design, the frogs may or may not be able to see or hear the fish.