Aquarium Livestock Pet Care Guides

Sea Slugs & Nudibranchs

Natural Habitat

Indo-Pacific, Atlantic

Tank Temperature




Specific Gravity


Tank Requirements

Requires pristine water conditions; put mesh covers over drains, powerheads, and pump intakes.


Largely unknown for most species. They are thought to specialize on some sponges, tunicates or corals. Sea Hares will graze on algae and need to be fed if there is not enough algae in the aquarium.


Some release inks into water when stressed (mostly the Sea Hares); peaceful; some graze on algae and invertebrates like sponges and corals.


Generally Reef and Invert Safe, although some may eat sponges, tunicates and some corals. Use caution since most nudibranch diet is largely unknown. Do not keep more than one nudibranch to a tank.

Species Overview

The term "nudibranch" means "naked gill" and refers to the fringy, tassel-like gills visible on many species. This group include animals that we commonly refer to as "sea slugs" as well as the sea hares popular for algae control. As a group, there is not much known about many species of nudibranch and more are being discovered and reclassified continuously. While some like the sea hares are well studied and we know enough about their life cycles and diets for them to be maintained, the diet and requirements of most nudibranchs is largely unknown. Most are thought to feed on sponges, polyps, tunicates. Some of the most colorful nudibranchs are actively collected and sold for aquariums but many more come as "hitchhikers" on rock and corals, for better or for worse.

Although there are many types of sea hares in many marine environments, most are green or brown, usually with darker markings that make them look like algae-covered rocks. The name "Sea Hare" comes from their vegetarian diet as well as the two fringes on their head that look like rabbit ears, especially when the animal is lifting the front of its body and looks like a rabbit sitting up on its back legs. Sea Hares are sought after for their voracious appetites, feeding on macro and filamentous algae. They will feed on dried algaes if the live algae supply dwindles and should be fed to avoid starvation. These slugs are reef safe and will not eat corals or polyps, but their size makes them cumbersome in smaller aquariums. The Aplysia genus includes some of the larger sea hares, most of which grow to about 6-8 inches in length.

Use caution when placing any nudibranch in your reef system if its diet is an unknown. Nudibranchs in aquariums are generally shortlived, both due to their natural short lifespans as well as the difficulty of meeting their dietary requirements. If stressed, a sea hare may release a blue-purple ink into the water. While unsightly and irritating to some sensitive organisms, the aquarium's filtration system will usually take care of removing this ink. A water change will also help remove it from the aquarium.

We always suggest that you do further research before adding a new pet to your tank. What we have provided for you are guidelines and suggestions. If you have any further questions or concerns, please contact our fish room at 717-299-5691 ext. 1213 or

Recommended Items

Invertebrate Food
Testing Equipment