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Post  phantom on Sun Jan 23, 2011 1:49 pm

* 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 coralline growth available for them to feed on. If this is a concern, you might think about placing a few urchins in the sump to help remove excess coralline, micro and macro algae growth there.
* 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 destabilization 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 varieties here,
some common ones are
Blue Tuxedo (Pincushion) Urchin

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.

It 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.

Black Longspine Urchin, Long-Spined Sea Urchin

The Black Longspine urchin is a peaceful, easy to keep invert for your marine aquarium if you have a mature tank with plenty of coralline algae. The urchin is black with very long spines and has irridescent blue spots scattered around it's body. It also has an appendage which looks like a mouth but is the 'other end'. They will continuously graze in your tank. Often you can hear a scraping sound as it rasps away coralline algae. The urchin has long black spines which are not supersharp, but, can poke you if you are not careful when putting your hand in the tank. Most of the time it is shy. My urchin is out and about all day but many may become nocturnal and hide in caves during the day.
Like most inverts, this urchin is sensitive to high nitrates and copper. If it is stressed from poor water quality, it will drop it's spines.

pencil urchin

The Pencil Urchin of the Eucidaris genera has a brown and tan, sometimes mottled body with stubby, thick spines radiating out in all directions. Pencil Urchins are primarily omnivorous scavengers that will generally hide in rock caves or crevices during the day
This is a peaceful species that makes an excellent aquarium cleaner and provides a different look then the more common snail and crab aquarium cleaners.
Pencil Urchins eat both marine algae and meaty foods that it comes accross while scavenging the live rock and substrate of the aquarium. It is important to have a good amount of live rock for the Pencil Urchin to scavenge for food, as live rock provides a place for marine algae, sponge and other smaller invertebrates like sea squirts to live and grow. Pencil Urchins will also accept dried seaweed or meaty foods as a supplement food source.
Zoalogist AKA Zoa Addict
Zoalogist AKA Zoa Addict

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