Ecsenius bicolor: a Beginner-Friendly Blenny with Real Character

Bicolor blenny (Ecsenius bicolor)

Bicolor blenny (Ecsenius bicolor)

Included in the Indo-Pacific genus Ecsenius are several interesting, beginner-friendly, generally aquarium-worthy blennies, among them the popular bicolor blenny (E. bicolor). This species’ modest size and bottom-dwelling habit also make it a great choice for smaller aquarium systems.

Physical traits

Though by no means brightly colored, E. bicolor is attractive nonetheless. Actually, there are several color phases of this species, but the one you’re most likely to encounter has a bluish/purplish/brownish anterior (emphasis on “ish,” as characterizing this species’ color is not as straightforward as it might seem) giving way to an orangish-yellow posterior.

Its body is slender and almost eel-like, and it has a long, continuous dorsal fin; blunt head; high-set, bulbous eyes; and antennae-like cirri protruding from between the eyes. Its maximum length is approximately 4 inches. At the risk of anthropomorphizing this species, it can, perhaps, best be described as both droll and beguiling.


Bicolor blennyAs mentioned, E. bicolor is a small benthic species—typically found perched on the rockwork or hopping from rock to rock, intently rasping algae as it moves along. Therefore, it doesn’t demand a great deal of open swimming space. I’d put its minimum aquarium size at around 30 gallons. This species will typically choose a hole in the rockwork as its regular refuge, so be sure to provide a good amount of porous, holey live rock. Also, note that it’s best to introduce E. bicolor to a mature aquarium with a decent crop of microalgae to graze rather than a “sterile,” newly set up system.


E. bicolor is predominantly herbivorous, so in addition to providing grazing opportunities (natural microalgae growth) in the tank, a good mix of green foods, including various algae-based dried foods (e.g., New Life Spectrum® AlgaeMax pellets) and frozen herbivore formulations, should be offered.


The bicolor blenny is relatively peaceful, though it may squabble with perceived resource competitors, such as other blennies or species that are very similar in appearance or habits. Conspecifics are also best avoided unless you can be certain of acquiring a bonded pair.

It’s generally safe to keep E. bicolor in reef systems, but do keep in mind that, as is often the case with herbivorous species, it may nip at fleshy coral polyps and tridacnid clam mantles as it grazes over the rocks and substrate, causing them to retract their tissues, potentially with adverse health effects if the behavior persists.

Photo credit: Barbara Quinn, Sidney Sevilha


If you enjoyed this post, subscribe to get our new posts in your email.
About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. I love “Jerry” my bicolor blenny. He is exactly as you describe. He will greet you with enthusiasm, but won’t eat out of your hand. I bought mine with a big diamond goby named “Ben”. The two are buddies. He has his favorite hidey holes especially the ones with a warm and fuzzy crop of long hair green algae. :/ He just scoots his tail right in there and those big eyes just watch everything going on. Also, if bored he will eat mysis shrimp but only the tiny ones. Thanks for the post. Everyone should enjoy one of these guys.

    PS> Waiting on the Blue Velvet Damsel vs Your Stealth video. 🙂

    • Thanks for sharing, Kathy! And fear not, our damsel video is still on its way! We’ve managed to capture 3 of the 4, but there’s one smart-alecky holdout that seems to have gotten wise to our methods. We’re giving it a little time to let down its guard again before we have another go at it.

Speak Your Mind