Urchins :
If you are looking for a unique invertebrate to add to your saltwater tank, consider the sea urchin. Before you do, however, it is wise to learn a little bit about these creatures.
The sea urchin is a small, spiny animal that can be found in a variety of saltwater habitats. These creatures belong to the class Echinoidea in the phylum echinoderm which contains over 900 different species. Many people are familiar with the sea urchin but they may not realize that they are actually living creatures. Not only are sea urchins a unique and interesting creature, but they also make a great addition to the saltwater tank.
If you are looking for a unique invertebrate to add to your saltwater tank, take the time to learn a little bit about these intriguing creatures to see if it might be the right choice for you. Keep in mind that there are many different species of sea urchin, so even after you make the decision to add a sea urchin to your tank you will need to research the particular species to determine its tank requirements. In this article you will learn the basics about sea urchins and receive tips for caring for them in your own saltwater aquarium.
About Sea Urchins
epending on the species, sea urchins range in size from 6 to 12 cm in diameter, though the largest recorded specimen measured 36 cm. These creatures are bilaterans which means that their bodies have bilateral symmetry, but most species develop fivefold symmetry as they mature. These species may develop five different parts of equal size that radiate from a central axis. Other sea urchins, like the sand dollar, are ovular in shape and have a distinct rear and front. The two halves of a sea urchin are typically divided into the lower half, called the oral surface, and the upper half, the aboral surface. The oral surface contains the mouth parts while the aboral surface contains the internal organs which are enclosed in a sac protected by fused plates of calcium carbonate. The most distinctive parts of the sea urchin are its spines which vary in length and are used to protect the sea urchin from predators. The length of these spines may range from 1 to 3 cm but some have spines as long as 10 to 30 cm.
Caring for Sea Urchins
The first thing you need to consider when adding a sea urchin to your saltwater tank is that you have enough space. You should plan to dedicate at least one gallon of tank space per inch of a sea urchin’s maximum size. These creatures may not take up a great deal of space and they do not move quickly, but they will contribute to the biological load of your tank. The ideal water temperature for a sea urchin may vary depending on the species but, for the most part, these creatures prefer a temperature around 80F. In addition to water temperature, the salinity of your tank is also important – you may want to research the specific needs of the species you choose but, in general, a salinity at or near that of sea water is preferable.
In addition to providing your sea urchins with the proper tank environment you also need to ensure that they have an adequate supply of food. In the wild, sea urchins feed on various types of algae including seaweed, kelp, laminaria and egregia. The preferred diet will depend on the species of sea urchin you select but you should be prepared to provide a variety of different types of algae to keep your sea urchin well-fed. Be careful not to overfeed your sea urchins, however, because any excess algae or vegetable matter in the tank could result in a build-up of harmful toxins like ammonia which could contribute to a decrease in water quality.
Other Things to Know
In addition to feeding your sea urchins you should also make sure to keep the tank clean. If you are adding a sea urchin to an existing saltwater tank you should already be performing routine water changes to keep the water quality in your tank high. As you perform your routine water changes, be careful not to disturb your sea urchins and be sure not to damage their spines when using an aquarium gravel vacuum. You should also keep in mind that sea urchins may not be compatible with all of the species of fish you have in your saltwater tank. Certain species of fish like triggerfish will prey on sea urchins and are thus not compatible. Starfish may also pose a danger to sea urchins.
Sea urchins are a great addition to the saltwater tank.
Types of Sea Urchin :
There are hundreds of different species of sea urchin out there, but not all of them are recommended for the pet trade. Below you will find a list of some of the best sea urchin species to keep in the saltwater tank:
Blue Tuxedo Urchin – The blue tuxedo urchin is a very peaceful species that only grows to about 3 inches in diameter. This species is easy to care for, though it does prefer warm waters between 72°F and 78°F and a pH range between 8.1 and 8.4. Blue tuxedo urchins are herbivorous and they may graze on the algae in your tank. This species does not tolerate high nitrate levels and it may require supplements of calcium, magnesium, iodine, and trace elements.
Black Longspine Urchin – This sea urchin is named for its black color and long spines – it generally grows to a diameter of about 10 inches. The black longspine urchin is native to the Caribbean and it is generally peaceful in the home aquarium. These urchins prefer water temperatures between 72°F and 78°F with water hardness between 8 and 12 dKH and pH between 8.1 and 8.4. There are also green, blue, and white color forms of the longspine urchin.
Pencil Urchin – The pencil urchin looks a little different from other urchins because its spines are much thicker. This species grows to a diameter around 5 inches and it comes in black, red, white, and tan. The pencil urchin is an omnivorous species, feeding on algae and small invertebrates. It prefers water temperatures between 72°F and 78°F with a pH between 8.1 and 8.4.
Shortspine Urchin – The shortspine urchin grows to a maximum diameter around 3 inches and it has hundreds of uniform reddish-orange colored spines. This species is peaceful by nature and reef compatible – it is also fairly easy to keep in the home aquarium as long as you provide plenty of live rock for grazing. The shortspine urchin cannot tolerate poor water quality or high nitrate levels.
By now you should have a basic understanding of what sea urchins are and what roles they can plan in the saltwater aquarium. Keeping sea urchins in the home aquarium is no easy task but, if you prepare your tank properly and if you are careful in selecting a species, you can be successful in keeping sea urchins as pets.
Urchins- List of species :
Sea Urchins are approximately 2"-3" in diameter, with the spines extending possibly twice that distance. Care must be taken to prevent the Urchins from accidentally overturning rocks in the reef tank causing damage to themselves and other reef inhabitants such as live corals. Sea Urchins make great additions to marine aquariums, consuming undesirable algae and detritus within the tank.
1-Blue Tuxedo Urchin
Mespilia globulus
Minimum Tank Size: 20 gallons
Care Level: Easy
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 3"
Color Form: Black, Blue, Red, Tan
Diet: Herbivore
Supplements: Calcium, Magnesium, Iodine, Trace Elements
Compatibility: View Chart
Origin: Indo-Pacific
Family: Temnopleuridae
The Blue Tuxedo Urchin, also known as the Sphere Urchin or Globe Urchin, has five to ten broad-colored bands usually blue or black, with red, brown, or dark spines. This very striking combination, gives it the "formal" look and thus the name "Tuxedo Urchin."
During the day, it will hide among the rocks, in crevices, or under plants in a sandy substrate. At night, it will emerge to graze on the algae present in or near its home. The Tuxedo Pincushion Urchin generally roams alone, but several of them could be housed in the same aquarium if it is large enough to provide them with adequate food (algae) and shelter. It is sensitive to high levels of copper-based medications and it will not tolerate high nitrate levels. If it starts to lose a number of spines, it is often due to poor water conditions.
If algae levels are particularly low, its diet will need to be supplemented with dried seaweed.
Approximate Purchase Size: Small 1-1/2" to 2" Medium 2" to 3"
2-Pincushion Urchin
Lytechinus variegatus
Minimum Tank Size: 20 gallons
Care Level: Easy
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 8"
Color Form: Blue, Purple, Red, White
Diet: Herbivore, Omnivore
Supplements: Calcium, Trace Elements
Compatibility: View Chart
Origin: Atlantic Ocean, Caribbean
Family: Toxopneustidae
The Pincushion Urchin has an oval to round body covered with hundreds of uniform spines. Its color can range from red to purple to white and blue.
t requires ample hiding places and sufficient room in which to forage in the home aquarium. It generally hides in caves during the day, though it may make a burrow in thick substrates. At night, it comes out to graze on algae, moving about by its suctorial podia that are aligned in five doubled rows. The aquarium should include large amounts of live rock on which it can graze. It may also prey on some of the sessile invertebrates in the reef system. Rock formations need to be stable and able to withstand the movement of the Urchin wedging itself in crevices. It is generally solitary, but will tolerate others of its own kind. It is sensitive to high levels of copper-based medications and will not tolerate high nitrates. Poor water quality will cause it to lose its spines.
It is extremely difficult to breed in an aquarium, with no distinguishing characteristics to help differentiate it from its mate.
If there is insufficient algae for it to graze on, the diet should be supplemented with dried seaweed.
3-Longspine Urchin, Black
Diadema setosum
Care Level: Easy
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 10"
Color Form: Black, Blue, Green, White
Venomous: Yes
Diet: Herbivore
Supplements: Calcium, Iodine, Trace Elements
Compatibility: View Chart
Origin: Caribbean, Fiji, Indonesia
Family: Diadematidae
The Black Longspine Urchin, also known as Long-spined Sea Urchin, has a body which is predominately black with a red eyespot in the center. The spines on these urchins are long, thin and completely black. They are a very delicate looking urchin, which are actually very capable of protecting itself. These urchins are excellent algae controllers for an aquarium housing aggressive fish.
Provide an aquarium with ample hiding places and room to roam. Being a nocturnal creature, the Black Longspine Urchin will hide during the day and only come out at night to forage for food such as algae and seaweed. These urchins are an excellent algae controller for an aggressive aquarium where other invertebrates would be eaten. When approached by a fish, these urchins will sense their presence, and will defend itself by directing its spines towards its offender.
It is very sensitive to high levels of copper-based medications and will not tolerate high nitrate levels. If it begins to shed its spines, it is a sign of very poor water quality.
Be aware, it is venomous, with its sting being roughly equivalent to that of a bee sting.
The diet may be supplemented with dried seaweed.
Approximate Purchase Size: Small: 1-1/2" to 2"; Medium: 2" to 3" Large: 3" to 4"
4-Pincushion Urchin, Hairy
Tripneustes gratilla
Care Level: Moderate
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Color Form: Black, Purple, Red, White
Diet: Omnivore
Supplements: Iodine, Trace Elements
Compatibility: View Chart
Origin: Indonesia, Maldives, Sri Lanka
The Hairy Pincushion Urchin is also known as the Sea Egg, and the Priest-hat Urchin. It has five or ten double rows of white and red spines separated by spaces of red, purple, white or black. To camouflage itself, it often covers itself with rocks, sponges, shells, or algae. In addition to camouflage, this provides shade, and in some cases, a food source. These urchins work wonders in aquariums that suffer from filamentous algae infestation, consuming this undesirable algae quickly.
It will generally do well in an aquarium if provided with ample hiding places and a large area in which to move. It prefers an aquarium with live rock so that it can graze on algae and it will even eat Caulerpa sp.. It should be housed with nonaggressive fish. It is sensitive to high levels of copper-based medications. Poor water conditions will cause it to shed its spines and rapidly decline in health.
It is extremely difficult to breed in an aquarium with no distinguishing characteristics to help differentiate it from its mate.
If there is insufficient algae for it to graze on, the Hairy Pincushion Urchin should be fed dried seaweed.
Approximate Purchase Size: Small: 1" to 1-3/4"; Medium: 1-3/4" to 2-1/2"
5-Pencil Urchin
Eucidaris tribuloides
Minimum Tank Size: 30 gallons
Care Level: Moderate
Temperament: Peaceful
Reef Compatible: No
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 5"
Color Form: Black, Red, Tan, White
Diet: Omnivore
Origin: Caribbean, Philippines
Family: Cidaridae
The Pencil Urchin of the Eucidaris genera is also known as the Mine or Club Urchin. It has a brown, sometimes mottled body with stubby, thick spines radiating out in all directions. The spines are surrounded by basal plates. Never try to pry it out of a hole, as you will break its spines before it lets go. As it ages, its spines may become covered with coralline and other types of algae.
During the day it will seek shelter in the rocks; at night it will come out and forage for food, looking particularly for algae lawns and smaller invertebrates like sea squirts or sponges. It can be destructive to corals. It requires an aquarium with multiple hiding places and live rock on which it can graze. The rock formations should be sturdy, since the Urchin could dislodge rocks as it moves around the tank. The Pencil Urchin is very sensitive to high levels of copper-based medications and will not tolerate high levels of nitrates. If water conditions are poor, it will shed its spines.
It is extremely difficult to breed in an aquarium and has no distinguishing characteristics to help differentiate it from its mate.
It should be offered dried seaweed and some animal-based supplemental foods.
Approximate Purchase Size: 1-1/2" to 3-1/2"
6-Longspine Urchin, Banded
Echinothrix calamari
Care Level: Moderate
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 9"
Venomous: Yes
Diet: Herbivore
Supplements: Calcium, Magnesium, Iodine, Trace Elements
Compatibility: View Chart
Origin: Indo-Pacific
Family: Diadematidae
The Banded Longspine Urchin, also known as the Longspined Urchin or Hatpin Urchin, has a black central body with long, sharp spines, sometimes reaching 9 inches in length. The spines have hundreds of alternating light and dark bands. Some spines are strong, thick, and hollow, whereas others are shorter and finer.
During the day it often hides in rocky crevices, and in the wild, can be found in large aggregations with other Banded Longspine Urchins. The aquarium should have stable rock work and some shaded areas. During the night, the Banded Longspine Urchin comes out to feed. Juveniles generally eat algae, and the adults are carnivores, preying on invertebrates. Smaller fish, such as the Banggai Cardinal, will often seek shelter among its spines during the day, leaving their protection at night to eat. It will not tolerate copper-based medications and needs low nitrate levels. If it begins to shed its spines, it is a sign of poor water quality.
Use care when handling the Banded Longspine Urchin, the spines are venomous; the sting from there spines are similar to a bee sting.
In the aquarium, food can be placed near its spines or even on them. The spines have the ability to transport the food to its mouth.
Approximate Purchase Size: 1-1/2" to 3-1/2"
7-Longspine Urchin, Blue Spot
Astropyga radiata
Care Level: Easy
Temperament: Peaceful
Reef Compatible: With Caution
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 8"
Color Form: Blue, Tan
Venomous: Yes
Diet: Omnivore
Origin: Indonesia, Maldives
Family: Diadematidae
The Blue Spot Longspine Urchin, also known as the Radiating Hatpin Urchin, has a magnificently colored body with bright electric blue spots outlining five bands from a central ring. The long, thin spines captivate the eye, banded tan and brown and endlessly moving as the urchin patrols the reef.
The Blue Spot Longspine Urchin makes an excellent algae controller for an aquarium housing aggressive fish. Provide an aquarium with ample hiding places and room to roam. The rock formations should be sturdy, since the Urchin could dislodge rocks as it moves around the tank. Being a nocturnal creature, the Blue Spot Longspine Urchin will hide during the day and only come out at night to forage for food.
When approached by most fish, these urchins will sense their presence, and will defend itself by directing its spines towards its offender. In the wild, these urchins sometimes provide shelter to a variety of other organisms including commensal shrimp, crabs, and cardinalfish that find solace from predators within the urchins' spines during daylight hours.
It is very sensitive to high levels of copper-based medications and will not tolerate high nitrate levels. If it begins to shed its spines, it is a sign of very poor water quality.
Be aware, it is venomous, with its sting being roughly equivalent to that of a bee sting.
The diet of the Lonspine Urchin, Blue Spot should consist of dried seaweed and some animal-based supplemental foods. If an ample food source is not present in the aquarium it may attempt to eat corals.
Approximate Purchase Size: Small: 1" to 2"; Medium: 2" to 3-1/4"; Large: 3-1/4" to 4-1/2"
8-Purple Short Spine Pincushion Urchin
Pseudoboletia sp.
Minimum Tank Size: 20 gallons
Care Level: Easy
Temperament: Semi-aggressive
Reef Compatible: With Caution
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 4"
Color Form: Black, Pink, Purple
Diet: Herbivore
Supplements: Calcium, Trace Elements
Compatibility: View Chart
Origin: Sri Lanka, Sumatra
Family: Temnopleuridae
Looking for a striking and easy-to-care-for addition to your cleanup crew? The Purple Short Spine Pincushion Urchin will scavenge over rock and substrate for bits of food and algae to eat while adding interest to your home aquarium.
Pincushion Urchins have oval or round bodies covered with hundreds of uniform spines. Though the spines are short, they are still sharp, and can puncture skin. During the day, it will hide among the rocks, in crevices, or under plants in a sandy substrate. At night, it will emerge to graze on the algae present in or near its home.
The Purple Short Spine Pincushion Urchin generally roams alone, but several of them could be housed in the same aquarium if it is large enough to provide them with adequate food (algae) and shelter. It is sensitive to high levels of copper-based medications and it will not tolerate high nitrate levels. If it starts to lose a number of spines, it is often due to poor water conditions.
If algae levels are particularly low, its diet will need to be supplemented with dried seaweed.
Approximate Purchase Size: Small: 3/4" to 1-1/4"; Medium: 1-1/4" to 2-1/4"
9-Red Tuxedo Urchin
Mespilia cf globulus
Minimum Tank Size: 20 gallons
Care Level: Easy
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 3"
Color Form: Black, Blue, Red, Tan
Diet: Herbivore
Supplements: Calcium, Magnesium, Iodine, Trace Elements
Compatibility: View Chart
Origin: Indonesia, Maldives
Family: Temnopleuridae
Looking for an easy-to-care-for addition to your cleanup crew? The Red Tuxedo Urchin will scavenge over rock and substrate for bits of food and algae to eat. The Red Tuxedo Urchins have oval or round bodies covered with hundreds of uniform spines. Though the spines are short, they are still sharp, and can puncture skin.
During the day, it will hide among the rocks, in crevices, or under plants in a sandy substrate. At night, it will emerge to graze on the algae present in or near its home. The Tuxedo Urchin generally roams alone, but several of them could be housed in the same aquarium if it is large enough to provide them with adequate food (algae) and shelter. It is sensitive to high levels of copper-based medications and it will not tolerate high nitrate levels. If it starts to lose a number of spines, it is often due to poor water conditions.
If algae levels are particularly low, its diet will need to be supplemented with dried seaweed.
Approximate Purchase Size: Small: 1" to 1-1/2"; Medium: 1-1/2" to 2-1/2"
10-Shortspine Urchin
Echinometra sp.
Minimum Tank Size: 20 gallons
Care Level: Easy
Temperament: Peaceful
Reef Compatible: Yes
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 3"
Color Form: Black, Purple, White
Diet: Herbivore
Compatibility: View Chart
Origin: Caribbean, Indonesia
Family: Echinometridae
The Shortspine Urchin, or Rock Burrowing Urchin, has an oval to round black body covered with hundreds of uniform, reddish-orange spines. Typically found in the back reef, this night-dwelling algae cleaner is known to burrow small niches in carbonatic rocks (dead corals) to hide.
The Shortspine Urchin requires ample hiding places and sufficient room in which to forage in the home aquarium. It generally hides in caves during the day, though it may make a burrow in thick substrates. At night, it comes out to graze on algae, moving about by its suctorial podia that are aligned in five doubled rows.
The aquarium should include large amounts of live rock on which it can graze. Rock formations need to be stable and able to withstand the burrowing movement of the Urchin wedging itself in crevices.
Shortspine Urchins are generally solitary, but will tolerate others of its own kind. It is sensitive to high levels of copper-based medications and will not tolerate high nitrates. Poor water quality will cause it to lose its spines.
If there is insufficient algae for it to graze on, the diet should be supplemented with dried seaweed.
Approximate Purchase Size: Small: 3/4" to 1-1/4"; Medium: 1-1/4" to 2"; Large: 2" to 3"
Sea Urchin Facts: 18 Facts about Sea Urchins