The Blue Lagoon

Clear shallow water and relative calm characterize the lagoon. Here live some of the most lovely species collected for the aquarium. Lagoons often have a floor of sediment with tiny patch reefs dotted here and there. This diversity of topography and bottom type result in a correspondingly diverse fauna and flora.

Aquarium Capacity 75 gallons

Life Support live rock, live sand, standard reef filtration

Lighting two 150-watt metal halide lamps

Background deep blue

Decoration none

Special Requirements reef water conditions and moderate current

Fish

Calloplesiops altivelis 1

Gobiodon okinawae 5

Pseudocheilinus tetrataenia 1

Or Pseudocheilinus hexataenia 1

Invertebrates

Algae snails 7

Brittle stars 3

Trachyphyllia 3

Or Cynarina 3

Lobophyllia 1

Tridacna crocea 3

Seaweeds

Penicillus 5

Udotea 1

Cymopolia barbata 1 clump

Or Halimeda 1 clump

140 Saltwater Aquarium Models

140 Saltwater Aquarium Models

Few marine fish can compare with the comet grouper (Calloplesiops) in terms of hardiness and ease of care. It is rarely afflicted with parasites, even when other fish in the tank are. In a well-established reef community with plenty of live rock and live sand, the comet can find plenty to eat even without the attention of the aquarist. Its only drawback is a tendency to hide for a long time, even several weeks, after relocation. The primary requirement for success, therefore, is the presence of an adequate cave into which the comet can retire.

Keep the comet cave in mind as you select live rock for this model design. You are going to build a small patch reef at one end of the tank, arranging it so the comet can move in. The rest of the tank will be left open. You will need at least three pieces of rock to make a base, then a fourth one for the top of the cave. Add up to three smaller pieces around the bases of the larger ones to help balance the composition. Place a one- to two-inch layer of sand on the bottom, surrounding the bases of the live rock. Use as much live sand as feasible. You want to establish a thriving population of small organisms as quickly as possible. Once the live rock has been placed, create a "forest" of calcareous seaweeds across the open area of the sand. Choose an assortment of varieties from those suggested, or if you prefer use only one species. Make sure the holdfast is present on Penicillus, Udotea, and Halimeda. Poke a hole in the sand with your finger and gently place the holdfast, burying it at the same depth it was growing, as evidenced by the bits of substrate still clinging to the holdfast and stalk. Cymopolia lies in clumps on the bottom, often unattached. Leave room among the groups of plants to place the specimens of Trachyphyllia.

While Trachyphyllia normally sits in sediment, Lobophyllia forms dome-shaped colonies attached to rock. Since the two cannot be allowed to come into contact, lest Trachyphyllia sting its tank mate, place the Lobophyllia specimen atop the live rock. That should keep it a safe distance from the other coral. Either of these large-polyp stony corals adapts well to aquarium care. They make good starter corals. Moderate but not forceful current helps them feel at home. Trachyphyllia, open brain coral, is a single, large polyp. The skeleton is a simple cone that sits, pointed end down, in sediment. As a result of this growth form, it is easily collected without damage, which may help to explain why aquarium specimens do so well. Cynarina, button coral, is also a single large polyp and can serve as a stand-in for Trachyphyllia. Another open brain coral, Lobophyllia, possesses "teeth" at the margin of the colony, which are lacking in Trachyphyllia or Cynarina. Lobophyllia colonies are groups of polyps, another difference from the other two genera.

Tridacna crocea typically inhabits shallow water and so can contribute its beautiful blue and green colors to this lagoon aquarium. Unfortunately, it is among the more difficult members of its genus. Ideally, purchase a specimen already attached to a piece of live rock, and place pieces of rock on either side of the clam. It lives on hard-bottom areas, often wedged into a crevice. You could substitute another species of clam, as the most commonly available ones live in shallow water and should do well under the same conditions recommended for T. crocea.

Both the corals and the clams need food. You can feed small bits of seafood to the corals. Try different products to see which ones are acceptable, then offer them in rotation to provide a balanced diet. They may be seen to consume particles of food added for the fish. The giant clams will benefit greatly from phytoplankton additions four or five times a week. Other plankton substitutes, as well as organisms produced by the live rock and live sand, should provide a diet on which the invertebrates will thrive.

Biotope Tanks 141

Biotope Tanks 141

Homegrown Bounty

The importance of microscopic and near-microscopic invertebrates that reproduce within the aquarium can scarcely be overstated. For many kinds of showy, colorful invertebrates, these organisms are an essential component of the diet. Live rock and live sand play numerous roles in the ecology of the aquarium, with food production being one of the major ones. In addition to tiny invertebrates, Eurythoe, a small orange bristleworm, usually becomes established in live sand. It performs valuable service as a scavenger as well as provides food for certain fish and crustaceans. Snails may deposit eggs that are eaten by other organisms, added value to their usefulness as algae grazers. Numerous sessile invertebrates may release their larvae, periodically providing yet another substitute for plankton. Spawning fish are likely to lose eggs or fry to other larger creatures in the same tank. While not likely to supply all of the aquarium's dietary needs, homegrown foods such as these likely provide valuable nutrients lacking in processed aquarium foods. Creating a refugium in the sump of your system helps maximize production of a host of food organisms.

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