Family Blenniidae - The Blenniesp>Its hard to generalize about blennies. Some are peaceful while others are aggressive. Some are active and others reclusive. Many are colorful, yet seemingly just as many are drab. There are charmingly small blennies perfect for the home aquarium, and there are monsters which can attain lengths up to 53cm. Many are reef safe, but some readily feed on coral. Some have scales and some are scaleless. Blennies inhabit fresh-, brackish and seawater. Some species live on the bottom while others spend most of their time at the top of the water column (or even above the surface). Most are shallow water species, but at least one lives at depths greater than 330 feet. Many species are diurnal while some are nocturnal. As we said, its hard to generalize about blennies.
Family Blenniidae, the largest blenny family, includes 53 genera and at least 345 described species ranging from the illusory saber-toothed blennies of the largely inappropriate genera Aspidontus and Plagiotremus to the very appropriate and personable species of the genus Ecsenius. Outside of the family Blenniidae, there are many blennies of the suborder Blennioidei worthy of consideration by the home aquarists including the Triplefin Blennies of the family Tripterygiidae, the Red-saddled Sand Stargazers from the family Dactyloscopidae and the Barnacle Blenny from the family Chaenopsidae.
Captive feeding of species in the Blenniidae family is generally not difficult. In the wild, blennies run the gamut from carnivore to herbivore to omnivore, and their feeding habits are about as diverse as the fish themselves. For example, the Combtooth Blennies have comblike teeth which they use to scrape and eat algae (and the invertebrates contained therein), while the Sabertooth Blennies (aggressive mimics of cleanerfish) eat the flesh of other fish. Some of the tube-dwelling blennies from the family Chaenopsidae (e.g. the Barnacle Blenny, Acanthemblemaria macrospilus) are planktivores. Despite this diversity of feeding habits in the wild, in captivity, many blennies will readily take to small morsels of live or frozen food and prepared foods consisting of protein and vegetable matter. For the herbivore blennies, try herbivore preparations, dried seaweed (Nori), and live macro-algae from your refugium. For the Omnivores, add frozen carnivore preparations with finely chopped marine flesh, mysis shrimp and brine shrimp.
The so-called Scooter Blenny (Synchiropus ocellatus), which is not actually a blenny at all, deserves special mention in regards to its diet. This fish, and other dragonets, require large aquariums (75 gallons or larger with live rock and live sand) that are at least 6-8 months old. These fish are incredibly difficult (if not impossible) to adapt to a captive diet, and they rarely accept anything but the tiniest of live foods (hence they need to be in an established system with a hefty population of pods). It may be worth trying to tempt them with frozen artemia (baby brine shrimp) as a supplement.
Blennies should be kept in a well aquascaped aquarium, preferably with live rock and definitely with plenty of crevices, caves and other retreats. Many blennies appreciate a sandbed, as some species are prolific diggers. Because they are relatively aggressive towards members of their own species (and even other species within the family) it is best to keep one blenny per tank unless the tank is in excess of 75-gallons. While aggressive towards their own, Blennies can be harassed or even preyed upon by other aggressive fish, and so it is best to keep them with peaceful tankmates.
In terms of diseases, blennies are generally susceptible to many of the same marine parasitic diseases and infestations from which other fish suffer. As usual, a blenny that is stressed is more prone to infection than one which is not stressed, so make sure you have addressed the requisite environmental factors for the particular species. Also keep in mind that blennies dont chew their food, and so they must be fed food no larger than that which they can consume whole.
In conclusion, blennies can add a lot of personality and behavioral diversity to a marine set-up or they can prove to be con-artists adept at wreaking havoc on your other livestock. You should always do your research before purchasing any fish, but this is particularly the case when it comes to blennies. Anyone who tries to paint the suborder Blennioidei with a broad brush is either not very knowledgeable or they are lying to you.