The optimal foraging theory states that organisms forage for food in such a manner that will maximize their net intake of energy, resulting in organisms obtaining food that is most available to them. Occasionally, this can lead to organisms rejecting larger or more nutritious food sources for food that will require less energy to consume. Diodon holocanthus, commonly known as balloon fish, live in tropical marine habitats and feed on local Eucidaris tribuloides sea urchin (slate pencil urchin). For our project, we observed the eating habits of D. holocanthus to see if it was consistent to the optimal foraging theory. We determined the amount of weight needed to crush the shell of sea urchins of various sizes and found that smaller urchins were easier to break open than larger sea urchins. We also found that D. holocanthus tended to choose smaller urchins as opposed to larger urchins, however more data is needed to confirm this finding. For the final part of our project, we began looking into the effect of spine length and D. holocanthus preference. Our results indicated that urchins with smaller spines were not only easier to crush but appeared to be preferred by D. holocanthus.