Live Food Cultivation

PHYTOPLANKTON CULTURES. Microalgae, believe it or not, are the aquarist s friend. Readers may take a moment to recover from the shock, since microalgae are widely regarded as the bane of the reef aquarium's existence. I earlier offered advice on the control of these organisms (in Chapter Five) and now I say that they are beneficial. Why?

The term "microalgae" is, of course, a broad category. Included are everything from single-celled free-swimming organisms that show a weird mix of plant and animal characteristics to filamentous and mat-forming types that can indeed become a scourge. Cyanobacteria, the so-called "slime algae," are perhaps the most notorious, and the methods for control of algae growth in the aquarium are primarily directed at these species. Diatoms, golden-brown cells encased in silica, dinoflagellates of the free-living variety (as opposed to the symbiotic zooxanthellae), and a few species of filamentous green algae (Cladophora being a commonly encountered example) may also cause problems. At least two species commonly regarded as macroalgae, Valo-nia and Bryopsis, can sometimes grow uncontrollably and may frustrate all attempts at eradication, only to finally disappear as unexpectedly as they arrived.

The vast majority of algae, however, are benign species that form the basis of the entire marine food web. In the aquarium, especially an aquarium in which nonphotosyn-thetic filter-feeding invertebrates are housed, these kinds of microalgae, collectively called phytoplankton, must be provided in order to achieve success. As Gerald Heslinga recently wrote, "Phytoplankton are the basis for the aquaculture food chain."1 Fortunately, cultivation of phytoplankton can be quite simple, if the aquarist follows a few guidelines.

Isochrysis, Dunaliella, and Chlorella are three species of phytoplankton often grown in laboratories and hatcheries as food for marine organisms. Rotifers, for example, are fed phytoplankton. Should you attempt your own phytoplankton culture, it is important to 1) work with pure cultures of known identity; 2) maintain the purity of the culture(s) via sterile techniques; and 3) keep records of feeding regimens, culture density when fed, and similar data. An explanation of these techniques is beyond the scope of this book, but hobbyists who are interested in pursuing this form of phytoplankton culture should consult such sources as Bold and

On the other hand, if the only interest is in producing a mixed culture of "green water" for feeding a tank of fan-worms or soft corals, then one of the experimental techniques mentioned below may be the best route to that goal. ROTIFERS. Rotifers are strange multicellular, but microscopic, invertebrates that have been used for years as a source of food for larval marine fishes, such as clownfishes. The

1 Gerald Heslinga, personal communication.

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species most often cultivated for this purpose is Brachionus plicatilis.^Yiis organism, which is easily maintained on a diet of cultured phytoplankton such as Isochrysis, might be regarded as the foundation of the marine fish aquaculture industry. Explicit instructions for culture of Brachionus can be found in Moe (1989), and various other references. BRINE SHRIMP. The brine shrimp, Artemia salina, is a common inhabitant of highly saline environments and is available year round to aquarists, either as live adult shrimp or as resting cysts. Newly hatched brine shrimp, called nau-plii, are an old-fashioned staple food for all types of aquariums. The resting cysts, or "eggs," are widely available. To hatch nauplii, place about 2 tablespoons of synthetic sea-water mix in a clean quart jar and fill with RO water. Add about Va teaspoon of cysts, then aerate vigorously. The cysts will hatch in about 24 to 48 hours, depending upon temperature. The nauplii are attracted to light, and a flashlight can be used to lure them to a convenient spot from which they may be siphoned out, strained through a fine mesh net, and fed to the aquarium.

To rear adult brine shrimp, a large shallow container, such as a child's wading pool, is filled with old aquarium sea-water and allowed to sit in a brightly lit area until the water turns green, indicating a thriving population of microalgae. To speed up the process, add a pinch of house-plant fertilizer to supply nitrate and phosphate for the algae. Nauplii are then added. They will feed on the algae and grow to adult size (about Vi inch) in about three weeks. AMPHIPODS. Amphipods are the tiny, transparent, shrimplike creatures that are sometimes seen scuttling around on the rocks in the aquarium, feeding on detritus. They are about V4 inch in length. To culture them as food for the aquarium, set up a tank with a heater and a large, box-type power filter or a canister filter. Fill the filter compartment with a large sponge block or polyester filter pads. Pack in as much of this material as possible without restricting water flow. Now fill the tank with water containing detritus siphoned from an existing aquarium—the more, the better. Start the filter running, adjust the heater to 75 degrees F, and add a few amphipods, also collected from an established aquarium. In about a month, the filter material will be teeming with amphipods, which can easily be harvested by removing some of the material and swishing it in a bucket of clear seawater. Pour this through a net to concentrate the amphipods, then feed them to the aquarium.

Aquarium and Fish Care Tactics

Aquarium and Fish Care Tactics

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