Large vs. Small rocks in Zoo Tycoon

In Zoo Tycoon the smaller rocks tend to get the animals happier because they are a fraction of a large rock and can hit their rock requirement without going over. However they are expensive.

What is cost effective, some large rocks, or many small rocks?

Solution 1:

How Zoo Tycoon handles rocks is a little odd. Small and medium rocks both satisfy the same amount of animal happiness. For example, a mountain lion in a certain sized exhibit will be happy with up to 40 small rocks (after that it will start displaying sad faces). The same goes for medium rocks. However, the game counts large rocks as the equivalent of 4 small/medium rocks. So 10 large rocks will fulfill the requirement.

Small rocks cost $55 a piece. Four of those together cost $220. One large rock (the equivalent of four small rocks) costs $150.

So to be the most cost effective, use just large rocks until the animal stops making happy faces. Then delete the last large rock and begin placing small rocks. If after 1 - 3 it stops making smiley faces, keep the small rocks. If after exactly 4 small rocks it stops the smilies, replace them with one large rock. Just never use medium rocks!

Here's the experimentation I did with multiple different exhibits if you want to watch it for proof: