Sponges are very simple organisms while at the other extreme, the tunicates are highly developed animals including a nervous system. Identification is often quite difficult for both of these groups as growth patterns are strongly affected by environmental conditions so shape and color can be quite variable. Both groups produce thin encrusting as well as lumpy shaped masses. In general the sponges are more colorful.

Orange sponges come in a number of forms. The Orange ball sponge (Cinachyra sp.) is a distinct ball shape while the encrusting orange sponge (Mycale laevis) and the orange lumpy sponge (Ulosa hispida) can have many shapes. There are also yellow boring sponges (Siphodictyon sp. and Clioa sp.) that can appear as yellow dots or an encrusting mass. Red encrusting sponge masses (Diplastrella sp.) offer another attractive type. Encrusting tunicates can also be found that include brown (Botrylis sp.), red, blue-grey (Tridemnum sp.), white (Didemnum sp.), etc. The most dramatic are the blue sponges.

Sponges may be a useful addition to reef tanks as they are filter feeders specializing in very small particles such as bacteria and smaller. Because they feed on such small particles, from several microns to less than a micron, they may not be competing with other filter feeders that eat zooplankton or algae. In theory they could reduce bacterial levels in the water taking out things that pass through the finest mechanical filters. One problem with sponges is that they don't ship well dry. In fact some are reported to do poorly if taken from the water even briefly.

Though plant-like in appearance, sponges are actually one of the most primitive animals in the sea. They belong to a group called porifera. Most of us are familiar with the dried colorless varieties that populate the kitchens and bathrooms of the world. But in the ocean, live sponges can be found in an infinite variety of colors and shapes. Most of them are relatively small, but some varieties can grow to over 6 feet in diameter. Sponges differ from all other marine invertebrates in that they have no true tissues or organs. Their structure is composed of simple aggregations of cells. The name porifera means pore bearer. The tissue of sponges encloses a vast network of chambers and canals that connect to the open pores on their surface. Sponges feed by drawing a current of water in through their pores, filtering out the nutrients, and then ejecting it out through an opening. Many sponges on the reef resemble some of the corals in shape and color, but upon closer inspection the difference is apparent. They are one of the many life forms unique to the ocean environment. Sea squirts are very similar to sponges in appearance. They belong to a group called chordata. They are usually found growing in clusters on rocks. Like sponges, they filter particles of food from the water by pumping it through tiny pores and then expelling it through a central opening.

Tube Sponge
(Callyspongia ******lis)
The Tube Sponge is one of the most common varieties of sponge to be found on the reef. It is distinguished by its long tube-shaped growths, and ranges in color from purple to blue, gray, and gray-green. Filtered water is ejected through the large openings on the ends. This is one of the few reef invertebrates that is blue in color.

Vase Sponge
(Ircinia campana)
The Vase Sponge is a common species found in the Caribbean off the eastern coast of Florida. It is characterized by a large bell shape with a deep central cavity. This sponge grows up to 2 feet wide and 3 feet high. It ranges in color from purple to red and brown, and is found attached to rocks near the sandy bottoms.

Yellow Sponge
(Cleona celata)
This small Yellow Sponge species is commonly found throughout the Pacific coastal waters of the United States. It is found growing in small colonies, and ranges in color from orange to bright yellow. This sponge and can be found encrusting rocks on the reef face.

Red Tree Sponge
(Haliclona compressa)
This bright red sponge species is very common throughout the Caribbean Sea. This sponge usually grows to a height of about 8 inches. This is one species that is easy to keep and can do relatively well in a home aquarium environment. These sponges require a moderate water flow and dim light to do well.

Common Sea Squirt
(Didemnum molle)
This species of sea squirt is very common on the reef, and is usually found in deep water. It can be found encrusting the rocks in large colonies. This squirt's leathery bag-like body has a white and gray or brown spotted exterior with a bright green interior. It is sometimes introduced into the aquarium on live rock.

Painted Tunicate
(Clavelina picta)
The tunicates are very similar to sea squirts. They take water in through a large opening where nutrients are filtered out. The water is then expelled through another opening. Painted tunicates are about 3/4 inch long and commonly grow in colonies. They are found in translucent red, purple, and yellow colors.