This post is part one in a series on design and behavior of reef fishes. Non-planktonic (i.e., not floating around) invertebrates on the reef are often active at night and hide during the day. While diving or snorkeling you may see one of two groups of invertebrate eaters on the reef. If you see a bunch of fish sitting in the shade or in schools or in soft corals doing not much of anything all day, then they're probably waiting to go invert hunting at night. Examples of fish that do this are soldierfish, grunts and many snapper. If a fish is going to be sticking its head into holes and rummaging in the sand all day, then it is also going to be very vulnerable to attack. Thus, the fish that specialize in invert hunting during the day usually have defenses that protect them from predation (e.g., spines or armor) and they are almost always alone (outside of mating) -- a school provides a lot of eyes that can look for predators, but too many fish will mean that the invertebrates are going to be more likely to run away and hide. Examples of daytime, invert-eaters are trunkfish, cowfish, puffers, porcupinefish, triggerfish and filefish (I've included pictures of some of these). There are daytime invert specialists and nighttime invert specialists. One fish that I see on nearly every dive in Bonaire is the Smooth Trunkfish (this one is feeding on a huge pillar from the pier at the salt company). The trunkfish are fun to watch. They look very awkward when swimming and they're often blowing water into the sand to uncover little invertebrates. You can watch this behavior in this video.
I don't have a picture of a juvenile with me, but they are adorable, polka-dotted little cubes (here's a pic of one -- it's about the size of a pee). Similar species include a the spotted trunkfish (a pair of them here) and the Honeycomb Cowfish (note the horns).
Another daytime, invert-eater is a filefish. This orange-spotted filefish has a long dorsal spine sticking up for protection and, at this moment, is being pestered by a damselfish (as we'll see in many posts).