As well as marine fish you can keep a selection of invertebrates in your salt water fish tank aquarium. Invertebrates are creatures without backbones, many of which are aquatic and can be kept in a saltwater fish tank. This class of creatures include squids, lobsters, shrimps, starfish, sea urchins, sea anemones, coral and feather stars. Other marine invertebrates include sea squirts, sea cucumbers, zoo plankton, lugworms and sea hares.

Marine invertebrates suitable for keeping in a salt water fish tank include sea anemones, corals, sea sponges, crabs, shrimp and snails.

Sea Anemones

Anemones can be kept in a salt water aquarium provided excellent water conditions are maintained. they also require intense lighting and a strong current. They can be fed on blood worms, pieces of shrimp and other meaty scraps.

Although anemones are predators most of the species kept in fish tanks have a symbiotic algae (zooxanthellae) that will provide the anemone with nourishment as long as the lighting conditions are correct. if you place Tube anemones, Carpet or magnificent anemones in your fish tank ensure there is sufficient space between them as they will sting, and possibly kill, each other. Some mobile species may also damage live coral and anemones may also eat other invertebrates such as crabs and urchins or smaller fish.

Sea Sponges

Sea sponges are simple organisms of the Porifera phylum with over 5000 species known. They have only one type of tissue but specialised cells. Sponges feed by filtering water for microplankton. In the fish tank sponges must be anchored to rocks. they require absolutely pristine water conditions, with strong water currents and low lighting to prevent algae from growing on them. They must never be exposed to air. feed with special foods for marine invertebrates.

Crabs

Crabs can range in size from an inch to more than twelve inches. Some familiar species of crabs are Hermit Crabs, Porcelain Crabs and Boxing Crabs. Crabs will eat any edible materials they can find. Some species burrow deeply during the day so provide them with a deep substrate. Crabs need reasonably good water quality and are very good in the fish tank for their scavenger duties cleaning up algae and uneaten food.

Shrimps

Shrimps are a good addition to a salt water fish tank being colourful and also cleaning up left over food. Most shrimp are between two and three inches long with some species growing to more than ten feet in the wild. They remove parasites from fish and rely on camouflage and stealth for protection. They have a hard carapace which is shed regularly to allow the shrimp to grow. When shed the shrimp is very vulnerable until a new shell grows so in the aquarium provide rocks and caves for your shrimp to hide. they can be fed on flaked foods, freeze dried or live foods.

Snails

There are more than 40,000 species of snails and they are found in all aquatic environments. The families usually used in fish tanks are Mesogastopoda, Littorinidae and Haliotidae from the Caribbean and Pacific Oceans. They are mostly reef snails and vary in size from half an inch to around 8 inches in the wild. Snails are good additions to a fish tank as they are scavengers and eat algae. Place one snail to every two gallons of water to deal with the algae. Snails will also need a calcium supplement for shell maintenance and they are very sensitive to higher nitrate levels. Their diet can be supplemented by the addition of vegetable based tablet foods, blanched lettuce, or dried seaweed.

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