So nobody on RC has had one?
i had one for about a year, until i sold it to a teacher with a coldwater tank in his classroom (where it is still thriving). it was one of the most interesting fish i have ever had. very intelligent and attractive. they are indeed "aggressive," but this is really results from their intense territoriality-- they are otherwise shy (at least as juveniles) and would likely ignore tank mates that learned to avoid their turf (something possible only in a very large tank). Males are known to defend territory much more vigorously than females.
i ordered mine from reef hot spot. after gently repudiating them for holding them in tropical aquaria (and grossly misinforming customers about optimal temps), i requested that my two specimens (one was originally for the teacher) be sent without heat packs; both arrived (with heat packs) in water warmer than i would ever ship tropicals in. mine BARELY survived the shock of being transfered to my 57-59F tank-- the other specimen, which went to the teacher's tank, died within a day or so. despite the company's failure to follow one extremely simple, reasonable shipping instruction, they would only offer credit for the wasteful loss of this rather pricey fish. i would use extreme caution in dealing with the aforementioned company, at least in acquiring temperate species.
an abundance of rocky caves is critical to a garibaldi's happiness (especially juv's), and is probably more important than the presence of any macroalgae or kelp. sponge is an important part of its diet, supposedly even supplying the compounds needed for its pigmentation-- mine absolutely loved the frozen anglefish formula (the one with sponge) and seemed to be doing quite well on it, along with cyclopeez flakes and other goodies to vary its diet. this is a fish that is very fun to feed-- makes any cichlid look like a prissy eater. however, it was quite finicky during its first days in captivity and could only be induced to begin feeding by offerings of live brine shrimp and live blood worms.
hope this helps-- moral of my story-- an extremely gratifying species to keep, but don't even bother unless you are willing to provide a very large tank (and large chiller) for it.