or "sea squirts" are common in all marine
habitats, attaching themselves to virtually any fixed
object on a coral reef. To feed, they constantly filter
out bacteria and phytoplankton by passing a continuous
stream of water through their body. The larger of the two
openings is the mouth, or incurrent aperture, and the
smaller is the excurrent aperture. The water stream is
kept moving by the action of tiny cilia (hairs) that line
the inside of the tunicate body. Waste products are also
expelled through the excurrent aperture.
These tunicates are about 1 1/2 inches in length. In the Philippines, it's common to see five or more of these blue tunicates in small colony-like formations. When disturbed, tunicates draw up the incurrent and excurrent apertures, much like a drawstring around the rim of a bag.
I don't know what type of fish this is...it's so small I may not have seen it when I took the photo! I suspect it's a type of Triplefin.
Tunicate Identification: Rhopalaea crassa (not for absolute certain since many forms of different identifications are very similar)