Marine aquarium invertebrates

Marine invertebrates run from the reef clean-up crew to centerpiece animals in their own right: cleaner shrimp, snails and hermit crabs that handle algae and detritus, plus anemones, clams, urchins and stars. Each profile lists what the species needs and whether it is safe in a reef.

Tank size: 5–201 gal; 5 gal (20 L) to 201 gal (760 L); half the list needs 20 gal (75 L) or more
Temperature: 75–81°F; 24–27°C, most of the list
pH: 8.1–8.4; Most of the list
Difficulty: 60 easy; 30 medium · 28 difficult
Temperament: 94 peaceful; 18 mostly peaceful · 6 aggressive
Reef safety: 59 reef safe; 48 reef safe with caution · 11 not reef safe

118 species and 4 varieties

Start here

The marine inverts to start with

The skunk cleaner shrimp is marked beginner at 2.4 inches (6 cm) for 20 gallons (75 liters), and it cleans the fish and the hand that feeds it. The trochus snail is the grazer marked beginner, and the blue-leg hermit crab the scavenger, both for 11 gallons (40 liters). The bubble tip anemone is the host anemone with a track record, marked medium for 30 gallons (115 liters). The derasa clam is the giant clam marked beginner, a sand-bed clam for 40 gallons (150 liters). The tuxedo urchin grazes algae at 3.1 inches (8 cm) for 20 gallons (75 liters), marked easy, and carries a caution only because it carries frags around on its back.

The rule

What the reef marks mean for invertebrates

Every profile carries a reef mark. Reef safe means the animal leaves corals and its fellow invertebrates alone. Caution means it usually does but has a habit: an urchin that carries frags, a crab that picks at polyps when hungry, a starfish that eats sleeping fish. Not reef safe means it eats coral or fish as a matter of course, the chocolate chip star and the mantis shrimp among them. Beyond the marks, every invertebrate is drip acclimated, because a salinity swing kills it, and no copper ever touches the tank.

01
Reef safe
Leaves corals and other inverts alone
02
Caution
Usually fine, with a known habit on the profile
03
Drip acclimate
A salinity swing kills an invertebrate
04
No copper
Fish medications wipe out every animal here

The crew

The clean-up crew

The peppermint shrimp is marked beginner at 2 inches (5 cm) and eats Aiptasia. The cerith snail works the sand and glass, the nassarius snail lives in the sand and eats leftovers, both marked beginner for 11 gallons (40 liters). The emerald crab eats bubble algae at 2.4 inches (6 cm) with a coral caution. The scarlet reef hermit crab is the peaceful hermit at 1.6 inches (4 cm). The Mexican turbo snail is the heavy grazer at 2.4 inches (6 cm), marked easy. The clean-up crew list covers the rest.

Echinoderms

Urchins, stars and cucumbers

The long-spine urchin reaches 9.8 inches (25 cm) across and lists 50 gallons (190 liters), a grazer marked easy with spines that go through a glove. The purple urchin is the smaller grazer at 3.1 inches (8 cm) for 20 gallons (75 liters). The sand-sifting star cleans the sand bed at 4.7 inches (12 cm) and lists 53 gallons (200 liters), because a smaller bed runs out of food. The serpent star scavenges under the rock at 11.8 inches (30 cm) across, marked easy. The sand-sifting sea cucumber turns the sand at 7.1 inches (18 cm) for 20 gallons (75 liters). The chocolate chip star is marked not reef safe, because it eats coral.

Anemones and clams

The rock flower anemone stays where it is put at 3.9 inches (10 cm) for 20 gallons (75 liters), marked medium, and the maxi-mini carpet anemone is the same size and rating. The long tentacle anemone reaches 15.7 inches (40 cm) and hosts Clark's and pink skunk clownfish. The maxima clam is the giant clam with the colors, marked medium for 40 gallons (150 liters) on the rock under strong light. The crocea clam is the smallest at 5.9 inches (15 cm) and marked difficult for the light it needs. The squamosa clam sits on the sand at 15.7 inches (40 cm), marked medium.

Specialists

Showpieces and specialists

The harlequin shrimp is 2 inches (5 cm) of blue and white that eats only starfish, marked medium for that reason. The Berghia nudibranch is 0.8 inches (2 cm), eats only Aiptasia and starves when the Aiptasia is gone. The lettuce sea slug grazes hair algae at 1.6 inches (4 cm) for 11 gallons (40 liters). The giant feather duster filters the water with a 5.9 inch (15 cm) crown, marked medium. The sea apple is 7.1 inches (18 cm) of color, marked difficult, and it releases a toxin when it dies that can take the tank with it. The pom-pom crab carries a small anemone in each claw and stays under 1 inch (2.5 cm).

By the numbers

Smallest

Largest

Easiest to keep

Most peaceful

Fits a 20 gallon tank

Fits a 30 gallon tank

FAQ

Common questions

Which marine invertebrates are easiest?

The skunk cleaner and peppermint shrimp, the trochus, cerith and nassarius snails and the blue-leg hermit crab are all marked beginner. The tuxedo urchin and the serpent star are marked easy.

Are starfish reef safe?

The sand-sifting star and the Fromia star are marked reef safe. The serpent and brittle stars carry a caution, and the green brittle star catches sleeping fish. The chocolate chip and red knob stars are marked not reef safe because they eat coral.

Why did my invertebrate die after I added it?

Acclimation, most often. A snail, shrimp or starfish dropped into water of a different salinity dies within days. Drip acclimate over an hour, and check that no copper medication has ever been used in the tank.

What eats Aiptasia?

The peppermint shrimp, marked beginner, and the Berghia nudibranch, which eats nothing else and starves once the Aiptasia is gone.

Can I keep an anemone with a clam?

Yes, with room between them. An anemone stings whatever it touches and walks until it settles, so the clam sits well outside its reach.

Do sea urchins eat coral?

No. They graze algae and coralline off the rock. The caution mark on most urchins is for what they knock over and carry: a tuxedo urchin will walk off with a frag on its back.

Index