Scientific name: Halimeda spp. Common Names: Halimeda, Money Plant, Large Leaf Watercress Algae Geographic Origin: Ubiquitous in tropical seas; Hawaii Type: Calcareous macroalgae Maximum size: Upward growth, up to 10 cms Lighting Required: moderate, 10-12 hours/day Temperature: 72-82 F, stability more important than exact temp Water Chemistry: pH 8.0 - 8.3, temps 72-83 and stable, s.g. 1.023-1.025, Ca2+ 400ppm Growth rates: Slow Demands: Moderate Care: Halimeda is a beautiful macroalgae of the calcareous type. This means that the fronds are stiff and incorporate calcium into their coin-shaped structures. Like Chaeto, Halimeda are from the division Chlorphyta, or green algaes. There are several species of Halimeda including: H. discoidea [*]H. opuntia [*]H. lacrimosa [*]H. monile [*]H. incrassata [*]H. copiosa, [*]H. tuna, H. discoidea [*]H. goreaui The two most common species that you will run into are H. discoidea and H. opuntia. Unlike many macroalgaes, Halimeda is relatively safe to put in the main aquarium as it tends NOT to be invasive. It prefers a sandy bed, moderate light and moderate water flow. If it's needs aren't met, the plant will begin to bleach and turn white. Since it incorporates calcium, it is important to maintain good levels in the water column. The also will require some iron. Recommendations include a level of 0.05ppm. Like many things in our marine aquariums, these plants require low nitrates and phosphates. Similar to chaeto, few animals will eat Halimeda except for one echinoderm, an urchin called Clypeaster rosaceus . Once Halimeda are doing well, they can be used as indicators of water quality. If conditions deteriorate, so will the plant. In my early days, I attempted to keep my halimeda in the refugium without success. Note the blanching. Later, was transplanted to the main aquarium.