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What is a Molly Miller?

J.L. Drede
J.L. Drede

A molly miller is a type of fish found in the Gulf of Mexico, along the southern Mediterranean, and the Pacific around Japan and Taiwan. Its scientific name is Scartella cristala, and it is part of the Blennidae family of fish. Like many other fish in that family, it is sometimes called a combtooth blenny. It is usually brown or olive in color with white and black areas covering its body and fins. The notable features of the fish tend to be its large eyes and the short hair-like appendages that cover its head — much like a mohawk haircut.

The molly miller is a tropical fish and it can be found in warm waters across the globe. It is a reef-associated fish and prefers shallow depths. The molly miller is rarely seen in depths below 32 feet (10 meters). Rocky areas and tide pools are common habitats for the fish, although it may also make beds of algae its home. In the wild, it is herbivorous and survives mostly on a diet of algae and other plant life. It is harmless to humans, and there is no market for the molly miller as a food fish. Commercial interest in the fish is limited to aquariums and fish stores.


Molly millers are somewhat popular for marine aquarium enthusiasts. Optimal conditions for a tank with a molly miller can be difficult to maintain however, so many aquarium experts recommend only experienced fish handlers attempt putting a molly miller in their tank. A tank for a molly miller should have plenty of hiding spots, including coral, rocks and thick plants. In aquariums the fish usually grows no larger than 4 inches (10 cm) in length, so a 30-gallon aquarium should be suitable. It makes a good fish for a community tank, but it should not be kept with other molly millers or fish that are similar in shape and size. It may view them as a threat and attack.

Both plant food and crushed crustaceans are suitable for its diet, although seaweed or algae should supplement it. Water temperature needs to be between 72 and 78 degrees Fahrenheit (22 to 25 Celsius), and the pH must be between 8.1 to 8.4. Assuming the tank conditions are suitable and the fish is comfortable, it will spend most of its time near the bottom of the tank, in areas with low to medium light.

Frequently Asked Questions

What is a Molly Miller?

A Molly Miller is a small, adaptable species of blenny fish scientifically known as Scartella cristata. It thrives in shallow marine environments and is recognized for its distinctive mottled pattern and crest of cirri on its head. This fish is a master of camouflage and plays a significant role in controlling algae in its habitat.

Where can you find Molly Miller blennies?

Molly Miller blennies are commonly found in the warm coastal waters of the western Atlantic Ocean, ranging from New Jersey in the United States to Brazil, including the Gulf of Mexico and the Caribbean Sea. They inhabit rocky reefs, jetties, and pilings, often seen darting among crevices and seaweed.

What do Molly Miller blennies eat?

Molly Miller blennies are omnivorous, with a diet that includes a variety of algae and small invertebrates. Their feeding habits help maintain the balance of the ecosystem by controlling algae growth and contributing to the health of coral reefs. They use their sharp teeth to scrape food off rocks and other surfaces.

How do Molly Miller blennies reproduce?

Molly Miller blennies are oviparous, meaning they lay eggs. During breeding season, males become territorial and prepare nesting sites to attract females. After spawning, the male guards the eggs, which are attached to the substrate, until they hatch. This parental care ensures a higher survival rate for the offspring.

Are Molly Miller blennies important to their ecosystem?

Yes, Molly Miller blennies are considered a keystone species in their ecosystem. Their grazing on algae prevents overgrowth, which can smother coral reefs and other marine life. By maintaining the balance of algae, they support biodiversity and the overall health of the marine environments they inhabit.

Can Molly Miller blennies be kept in aquariums?

Molly Miller blennies can be kept in saltwater aquariums and are valued for their algae-eating habits. They are hardy and can adapt to life in captivity, but they require a tank with plenty of live rock and hiding places to mimic their natural habitat. Proper care and water quality are essential for their well-being in an aquarium setting.

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