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Starfish

Starfish are divided into three classes; Asteroidea that contains Sea & Cushion Stars, Ophiuroidea that contains Brittle, Serpent & Basket Stars, and Crinoidea that contains Feather Stars & Sea Lilies in the Subclass Articulata.

Even though some starfish species do eat algae and most are scavengers that come out at night to feed on detritus and debris, here are some other important things about them that need to be considered before buying one.

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Depending on the species, many ARE predatory animals that will often attack and eat a wide range of invertebrates such as other starfishes, urchins, sponges, anemones, soft and stony corals of all types, coraline algae, clams and other mollusks, crustaceans, and sometimes even unwary or sleeping fish. Some starfish will survive in an aquarium if fed bits of clam, shrimp or other meaty fares, even though this might not be their natural diet.

• Many species can grow to quite a large size, which can cause a problem with them disrupting other tank life as well as possibly toppling or rearranging live rocks and corals.

• Starfish inhabit many oceans from warm tropical to cooler water regions around the world, so make sure the type you are getting is suitable for the tank temperature you have.

• Inspect any starfish before buying it to make sure it is healthy. A limp or weak specimen is a poor choice, and even though some may recover over time, most do not. Prospects should be active, moving and full-bodied, and with sea star species the tube feet should be visible. A good test is to turn the starfish over on its back and see if it rights itself. Also be wary of wounds that appear to be fresh where arms are missing, as these are potential sights for infection or disease. For more details about what to look for when buying starfish, we suggest reading the “Selection” section of Robert Fenner’s “Sea Stars, Class Asteroidea” article.

• To keep starfish in top condition in an aquarium, water quality should be excellent and nitrate levels very low, preferably unmeasurable.

When it comes to buying a starfish, or any livestock for that matter, it is important to thoroughly research any particular species, BEFORE you buy it! That being said, refer to our following starfish class profiles to learn more about the natural history, ecology, biology, and other characteristics of species found in each group.

Sea Urchins

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  Sea urchins are used as indicator organisms in public aquariums to determine if the system is functioning properly? Because these animals are so “picky” about water quality and cleanliness in an aquarium, they are the first to show signs of stress, seen when their spines are laying down or falling off.

• There are numerous varieties found in both tropical and colder water oceans around the world?
• Urchins are generally referred to as Wana (sounds like vawna) in Hawai’i?
• It is not unusual for some urchins to house tiny, species associated shrimps within their spines?
• Triggerfishes and Puffers will pick the spines off sea urchins, turn them over, then break open their shells to eat them?
• Prior to the early 1970’s, sea urchins in California were considered nothing more than pests, but now the export value of California’s sea urchin fishery is a multi-million dollar industry?
• Many species enjoy eating coralline algae? This is not necessarily bad, unless you place too many in number and/or of large size in a tank where their appetite can exceed the amount of coraline growth available for them to feed on.
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  If this is a concern, you might think about placing a few urchins in the sump to help remove excess coraline, micro and macro algae growth there, like John Rice did with some Variegated Urchins (Lytechinus variegatus).

• Some species are particularly predatory, and many do not eat algae at all?
• Long-spined members of the Family Diadematidae, such as Diadema and Echinothrix species, have venomous stinging spines?
• Large growing species can be cumbersome and act like little bulldozers, causing damage and the rearrangement or destablization of rock and coral scapes?

Now, with so many similar or closely related species found world wide, urchins can be difficult to identify, and even though a lot of these animals can be algae eating machines, as you can see some do not have positive traits. The bottom line about picking out sea urchins is to be careful of what kind you are really getting. Being too large in number to try and cover all the varieites here, we are going to profile some of the more common species.Pencil Urchins

These urchins are so named for the pencil shape of their spines.

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  • Some Pencil species, such as the Caribbean species Eucidaris tribuloides, are meat-eating animals, says Ronald Shimek in his There’s No Reason To Be Spineless article. He states that, “Before I found this out in my own system, I watched a Pencil Urchin (Eucidaris tribuloides) catch and eat a scarlet cleaner shrimp”.
  • A member of the Family Echinomertridae, the Hawaiian Pencil Slate or Slate Pencil Urchin (Heterocentrotus mammillatus) is one of our favorites because of its beautiful smooth, blunt ended, brightly red colored spines. Whether or not this species is completely reef safe is questionable, but we know that it is not an easy urchin to care for, not living long in captivity unless a plentiful supply of algae is provided.
  • Members of the Family Cidaridae are often referred to as Pencil Urchins, but these species have blunt, well-spaced primary spines, ringed at the base by smaller secondary spines, and the primary spines are often covered with algae and detritus. The Hawaiian Rough-Spined Urchin (Chondrocidaris gigantea) grows quite large to four inches in diameter with six inch long spines, while the Ten-Lined or Sputik Urchin (Eucidaris metularia) grows to a diameter of four to five inches, and the Thomas’ Urchin (Actinocidaris thomasi) to only about one inch.

Collector Urchins These urchins get their name from the trait they have of picking up and “collecting” objects, such as leaves, small rocks or pebbles, coral rubble, plant matter, and just about anything else they can find to camouflage themselves with. They come in an array of colors from light pastels to black.

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  • The Black Collector Urchin (Tripneustes gratilla) is commonly seen in Hawai’i. It spends its time on the reef slowing cruising around rocks and corals searching for algae to eat, and grows to about five inches in size. This urchins will cruise around on the glass and roam the aquarium in search of algae to eat.
  • Mentioned earlier, the Variegated Urchin (Lytechinus variegatus) is yet another type of collector urchin.
  • Once again referring to Ronald Shimek’s There’s No Reason To Be Spineless article, he states that one of his personal favorites is the Blue Tuxedo or Royal Urchin (Mespilia globulus) found in Palau that seldom exceeds 3 cm in skeletal diameter. John Rice states that it is an excellent herbivore, is small and does not disturb other corals or other inhabitants. It likes to cruise the rock work eating microalgae and some coralline. Besides, with its beautiful royal blue color, its quite an eye catching urchin.

Shrimp

Shrimp are not algae eaters, but natural scavengers. For this reason they make good tank cleaners.

They are best kept singly or as a mated pair. Some species will pick at other invertebrates and soft corals, and some larger species may attack fish, so be careful about which type you put in your tank.

• Most sought after are Cleaner Shrimps of the Lysmata species, particularly the Pacific Cleaner Shrimp (Lysmata amboinensis) and the Scarlet Cleaner Shrimp (Lysmata debenius), also known as a Red or Fire Shrimp. These little shrimp not only help to keep the tank cleaned as a good scavengers, but are fish parasite pickers and are used in reef tanks for controlling saltwater ich.

• The Coral Banded Shrimp (Stenopsus hispidus), also known as Banded Coral or Boxer Shrimp, is very popular. Aside from being excellent scavengers, they are pleasant to look at with their red and white stripes, and are considered reef safe. Some aquarists express concerns about this shrimp, because some say they have seen theirs attack fish. From our personal experiences with keeping many of these shrimp over the years, both in fish-only and semi-reef tanks, we have never had this occur. Coral Banded Shrimp are territorial and will “chase off” fish, but we have never seen one attack, catch or kill a fish. In fact, often they take up the task of cleaning fish, and even a Snowflake Eel, much like the Cleaner Shrimp does. This shrimp should only be kept singly or as a mated pair, because both males and females will fight each other, most often resulting in the death of one of them.

• The Clown or Harlequin Shrimp’s (Hymenocera picta) diet consists solely of the tube feet of Echinoderms in the Starfish Family. In Hawaiian waters we know that when you find a Harlequin Shrimp the small Linkia species of Comet or Blood Spotted Starfish will be close by, because this is its primary food source. It truly is one of the most stunning and colorful Shrimps, but rarely accepts other aquarium foods. Unless you have a good supply of starfishes for this shrimp to live on, it does not do well in captivity. If you have some prized starfishes in your tank, it is not wise to keep a Harlequin with them.

• The “true” Peppermint Shrimp (Lysmata wurdemann), not to be mistaken for the Camel, Camelback or Humpback Shrimp (Rhynchocinetes uritai), is a top reef tank janitor choice for controlling Aiptasia sp. anemones, and is another excellent scavenger. Even though the R. uritai is also a good tank cleaner, it is known for its fondness of Corallimorphs (Mushrooms) and Zoanthids, so this should be considered if you have these types of soft coral species in your tank.

• The Anemone or Pacific Clown Shrimp (Periclimenes Brevicarpalis) is a small shrimp of only one inch in size that has a symbiotic relationship with Sea Anemones and Clownfishes. This shrimp is said to be a reef safe tank cleaner that lives in a host anemone’s stinging tentacles, feeding or scavenging on food scrapes along with the Clownfishes.

Hermit Crabs

Did you know that hermit crabs are scavengers? Yep, most species will eat just about anything they can find. For this reason, they make ideal cleaners for a reef tank, as long as you choose a Reef Safe Hermit Crab.Properly chosen hermit crabs should have no negative impact on a reef system.

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In fact, they should are solely beneficial. Small species that do not grow more than a couple of inches in size are most desirable, as they usually do not disturb other tank life, and they are able to get into tiny cracks and crevices where algae grows that larger hermits cannot access. They can also access spaces under rocks and corals where detritus or debris accumulates to remove it.

Large species such as the Anemone Carrying Hermit (Dardanus pedunculatus), Yellow Hairy Hermit (Aniculus maximus) and Cone Shell Hermit (Trizopagurus strigatus) are undesirable as reef janitors, as they may cause unwanted damage to your reef system. These types of hermits can disrupt tank life by climbing on everything, and because of the large clumsy, bulky shells they live in, cause the toppling of rockscape arrangements and the moving of corals. Besides, they may attack or eat other tank inhabitants. If you desire to keep large hermit crabs, do so only in a tank of suitable environment and size, and remember they will outgrow their shells. You need to provide them with new housing (larger shells) as they molt and grow, otherwise they may attack other shelled animals to get a new shell. One commonly imported species that has this trait is the Clibanarius vittatus, most often sold as the Striped Hermit Crab. Do you need shells for your hermit(s)? Here are a few suppliers you can check out.

Popular Algae Eating Hermit Crabs

• Small hermit crabs of the Genus Calcinus found in Hawaii are extremely efficient little critters. Some remain very small, only 1-1.5 cm in size, while other species in this group reach a length of less than two inches. Because of their tiny size, these hermit crabs can really get into those spaces of a reef tank that other hermits cannot.

• The Blue Legged Hermit (Clibanarius tricolor), as well as other similar species are quite popular, but some such as the Anomura sp. will kill Astraea snails to obtain their shells.

• The Red Legged Hermit (Clibanarius digueti) is said by some to be a much better algae eater than the Blue Legged Hermit, less aggressive, and has been reported to eat red slime algae.

• Aside from eating algae, the golf ball sized Blue Eyed Hermit (Paguristes erythrops) spends its time stirring up the top layer of substrate of the aquarium.

• The Scarlet Hermit Crab (Paguristes cadenanti) is one of the most popular hermits with reef keepers, because of its colorful appearance, and because it will eat all kinds of algae, such as red, green and brown slimes, as well as green hair algae.

Snails

First of all, learn how to identify and stay away from all types of predatory shelled snails. These are stinging, venomous animals that either bore holes into their prey and rasp out their flesh, or kill their prey with venom, usually injected by means of a harpoon, and eat the prey whole. The largest and most obvious of the venomous species are all in the genus Conus, whose venom is not only lethal to other marine life, but exceptionally lethal to humans! Snails in the predatory category are not generally sold in fish stores, but sometimes they can ride in as hitchikers with live rock collected in the wild.Three of the most common marine snail species used for controlling algae in saltwater aquariums and reef tanks are the Astraea/Astrea, Turban/Turbo, and Trochus/Trocus, with many varieties found world wide.

• According to Julian Sprung’s Reef Aquarium Manual, Volume One, Astraea sp. are the ideal snail to be placed in your aquarium as soon as ammonia and nitrite levels reach acceptable levels (less than 1 ppm). Introduced as soon as possible to a new aquarium, that has reached this cycling phase, these snails effectively limit the development of all microalgae. In other words, they are good at eating diatoms, but will consume red slime and green algae as well. The Astraea tecta found in Florida and Caribbean waters inhabits rocky inter tidal regions and is are said to be quite adept at removing alga films from rock surfaces.

• There are numerous species of Turbans, referred to as Turbo snails, and Trochus snails world wide that feed solely on algae, making them perfect candidates for algae control. These types of snails are less adept at dealing with irregular surfaces, so they usually divide their time between cleaning the glass and digging in the sand for detritus.

• Another good glass polisher is the tiny Black Nerite (Pipipi) snail (Nerita picea) found in Hawaii. It only reaches a size of about 1.5 cm, and spends its time living along the shallow rocky and coral rubble covered inter tidal regions of the shoreline, in cohabitation with small hermit crabs of Genus Caleinus. The N. picea likes to reside on the aquarium glass in search of algae to eat during night time hours, but will spend some time roaming around to aquarium. Close relatives are N. neglectus, that grows to the size of a thumbnail, and N. polita lives in the sand during daylight hours and grows to about 1-1/2 inches. These two speices like to crawl out of the aquarium, therefore, they are not good choices.

Why do you need Reef Janitors

What exactly are reef janitors? Well, whether you call them janitors, custodians, cleaners or what have you, the term reef janitors refers to a compilation of different kinds of crustaceans and invertebrates that act as nature’s little helpers by performing various cleaning tasks. Some are strictly algae eaters, others eat algae and consume detritus and debris off the ocean floor, while others are sand sifters and filter feeders. With the many tasks these little critters perform in nature, what better way to maintain a clean and tidy saltwater aquarium than to let them do the job for you.Tank janitors are considered a “must have” in reef tanks, and are by all means suitable for fish-only aquariums, but only as long as the janitors you choose are suitable for beginners (if you are just getting started in the hobby), and are compatible with the fishes and invertebrates (including corals) that you have or may be planning to keep in your particular type of system.

So, with such as vast array of crustacean and invertebrate species to choose from, how do you know which ones to get? To help answer this question, here are profiles we have compiled on some of the most common reef tank janitors that will help you better understand these animals, and which species within these groups may or may not be suitable choices.