AlgaeBlensArt
"Foods/Feeding/Nutrition:
These fishes are algae eaters par excellence, but not all algae. The vast majority of their diet in the wild is made up of filamentous green algae species... a bit of red (Rhodohphyte) and brown (Phaeophyte)... they don't eat all types (e.g. not "bubble", Family Valoniaceae), species, and almost entirely ignore Cyanophytes, aka Blue Green Algae... that despite its common name occurs in all colors, and shapes... blue, black, green, red... almost always slimy to the touch. Most types of prepared, meaty foods are ignored, or if taken, with not enough enthusiasm to support these fishes.
Often, with aging of a captive system, there will be a shift in the make-up of micro- and macro-life that predominates... and a valuable lesson for observant aquarists in the loss of fodder for such grazers as these blennies. The very best gauge of such incurring change is a thinning of said fishes... first in the gut area, but spreading to the upper flank musculature. Such changes can occur quickly, in days, and supplemented foods must be made available to prevent loss. Of most use are prepared foods in the form of sinking wafers and pellets that are largely algae-based. Various of these have been shown to be accepted with gusto.
Alternatively, cultured macro-algae, dried people-intended algae like Nori, Kombu... can be tried, and with familiarity are generally accepted as well. For true "die-hards" hoping to entrain natural behavior, "algae rocks" can be cultured elsewhere (as in a lighted sump) and rotated into the main system periodically. "