This species feeds on benthic crustaceans (amphipods, isopods, crabs), gastropods, and polychaete worms.

This patterning extends into the dorsal and pelvic fins and covers the entire surface of the fish's body.

The following was written about this in Holbrook et al.’s paper: “We expect that other reef fishes that require foliose understory algae will be adversely affected by the shading effect of giant kelp.

For example, the spotted kelpfish (Gibbonsia elegans) requires foliose understory algae throughout its benthic life.

Planktonic larvae recruit to understory algae, where older individuals remain to hide from predators and feed on small invertebrates (Stepien, 1986).

Carr (1989) found that populations of this species were adversely affected by giant kelp, again through the reduction of understory algae.

We suspect, however, giant kelp will affect the occurrence (presence-absence) of such species as striped surfperch and Gibbonsia only when the forest is so dense that all appropriate understory algae are eliminated.”[8] A 2020 study performed by Ginther and Steele examined the impacts of an invasive species of algae–Sargassum horneri–on temperate reef fish, including the spotted kelpfish.

[9] The study concluded that reef fishes were hardly or not at all impacted by the invasive algae species, despite its widespread presence in many coastal areas.

The paper authors wrote, “our field experiment, in which S. horneri was completely removed from 6×6m plots on natural reefs, provided the most compelling evidence that fishes were not much affected by the invasive alga, given the lack of differences in fish density, species richness, diversity, and multivariate assemblage structure between plots with and without S. horneri.”[9] The spotted kelpfish feeds largely on epiphytic crustaceans, such as gammarid amphipods and flabilliferan isopods[7].

Spirontocaris picta was found to be the significant portion of Gibbonsia elegans' stomach content in one study.

These crustaceans are found on the same plants that Gibbonsia elegans live on, including brown and red algae.

In addition to crustaceans, polychaete worms and microgastropods have been found in abundance in the stomach contents of spotted kelpfish.

[10] The spotted kelpfish has been deemed economically insignificant to humans except for its contribution to the diet of certain game fishes.

[2] The giant kelpfish, Heterostichus rostratus, is another species of the family Clinidae that closely resembles Gibbonsia elegans.