One of the most unusual little creatures you rarely find at your local fish store is the Top Hat Blenny (Omobranchus Fasciolatoceps). Native to Southern Japan and the coast of China, the Top Hat Blenny inhabits estuarine and mangrove swamps near shore. There are over 900 species of Blenny that are known. The Top Hat Blenny is one of the few species of Blenny that is considered euryhaline and can tolerate an extensive range of water salinity similar to a molly that can live in fresh, brackish, or marine. However, they are more likely to be found in fresh or slightly brackish water than fully marine.
There is very little research on Top Hat Blennys compared to other fish, so there is some controversy on what habitats are ideal for them in captivity. They inhabit both fresh and brackish water in the wild, but it is not known if they can inhabit freshwater their whole life.
These adorable little guys max out at a whopping 3" in length so they can live happily in a 10 gallon aquarium. If you plan to house them in groups, a slightly larger aquarium like a 20 long is recommended because they can be territorial. Top Hat Blennys are bottom dwellers, so you want a soft substrate like sand. They spend most of their time hiding with just their little heads sticking out, using rocks and driftwood to create small caves. Sometimes, you will see them dig little nooks in the sand under rocks to hide. They are not very demanding because they can adapt easily, but it is important to keep up with your regular tank matanice. If you are housing your Top Hat in freshwater, you can keep your water hardness moderately high.
Top Hat Blennies are relatively easygoing, so in a brackish water aquarium, they can be housed with peaceful brackish species like Mollies and Mono Fish. In freshwater, they get along with most similar sized community fish like some tetras, platys, and danios. They are territorial, so other bottom dwelling fish that also like to hide in caves may get nipped at if they try to intrude. If you decide to keep a group of top hats, try to keep many different caves so that they do not fight over hiding spots.
Male Top Hats have a more prominent crest on their head, while females are smaller and have brighter colors. They can breed in fresh, brackish, or marine water, but the hatch rate is lower when in freshwater. When they are ready to breed, the male will choose a cave or hole where he will dance in front of the opening to attract a female. Once the eggs are laid, they will stick to the sides of the cave, where the male will guard them until they hatch.
Thankfully, Top Hat Blennies are not known to be picky eaters. They are omnivores and bottom feeders by nature, so you want to give them a variety of foods like live black worms or frozen worms as well as sinking plant based foods like Repashy or algae wafers. Variety is important for meeting their dietary needs and keeping them healthy.
A cute size and personality, it's surprising not to see these rare and unusual fish on every aquarium hobbyist wish list. Their attractive crest gives the illusion of a top hat while they sport zebra like stripes on their face. Top Hat Blennies are very hardy, low maintenance fish that add character to any aquarium.