- Kingdom: Plantae.
- Phylum: Chlorophyta
- Class: Chlorophyceae/ order: Bryopsidales
- Family: Udoteaceae
- Genus: Halimeda
- Species: Halimeda gigas (there is a wide variety of species)
Description: With a stem and holdfast, it anchors itself to the substrate by means of rhizoids. Its irregular, flat, oval segments join to other segments, forming chains or growing in clusters. It is rigid and calcareous because it contains calcium carbonate deposits.
Reproduction: By fragmentation and/or spores.
Habitat: Shallow sandy areas, intertidal zones, and shallow subtidal zones.
Distribution: Tropical oceans. Color: Light green. Size: Variable. Caution: None; if it dies, it leaves calcium deposits. Lighting: Moderate–High.
Natural predators: It is unpalatable to fish because it produces substances such as halimedatrial and halimedatetraacetate (Hay et al., 1988; Paul and Van Alstyne, 1988), and because of its high calcium content (Ogden and Lobel, 1978; Lobel and Ogden, 1981). However, Clypeaster rosaceus and parrotfish do consume it.
Physical removal: Remove manually.
Notes: It proliferates when Ca levels are high, consumes large amounts of calcium, and is a good natural indicator. It absorbs few nutrients. It does not tolerate high nitrate and phosphate levels or excessive pruning; when new segments develop, the oldest ones die.
SOME OTHER SPECIES Species: Halimeda bikiniensis W.R.Taylor, 1950 Species: Halimeda borneensis W.R.Taylor, 1975 Species: Halimeda cereidesmis Kraft, 2007 Species: Halimeda copiosa Goreau & E.A.Graham, 1967 Species: Halimeda cryptica Conlivaux & E.A.Graham, 1964 Species: Halimeda cuneata Hering, 1846 Species: Halimeda cylindracea Decaisne, 1842 Species: Halimeda discoidea Decaisne, 1842 Species: Halimeda distorta (Yamada) Hillis-Colinvaux, 1968 Species: Halimeda favulosa M.A.Howe, 1905 Species: Halimeda floridiana O.N.Dragastan, D.S.Littler, & M.M.Littler, 2003 † Species: Halimeda fragilis W.R.Taylor, 1950 Species: Halimeda gigas W.R.Taylor, 1950 Species: Halimeda goreaui W.R.Taylor, 1962 Species: Halimeda gracilis Harvey ex J.Agardh, 1887 Species: Halimeda hederacea (E.S.Barton) Colinvaux, 1968 Species: Halimeda heteromorpha N’Yeurt, 2006 Species: Halimeda howensis Kraft & J.M.Noble, 1994 Species: Halimeda hummii D.L.Ballantine, 1982 Species: Halimeda incrassata (J.Ellis) J.V.Lamouroux, 1816 Species: Halimeda kanaloana Vroom, 2006 Species: Halimeda lacrimosa M.A.Howe, 1909 Species: Halimeda lacunalis W.R.Taylor, 1950 Species: Halimeda macroloba Decaisne, 1841 Species: Halimeda macrophysa Askenasy, 1888 Species: Halimeda magnidisca J.M.Noble, 1986 Species: Halimeda melanesica Valet, 1966 Species: Halimeda micronesica Yamada, 1941 Species: Halimeda minima (W.R.Taylor) Hillis-Colinvaux, 1968 Species: Halimeda monile (J.Ellis & Solander) J.V.Lamouroux, 1816 Species: Halimeda opuntia (Linnaeus) J.V.Lamouroux, 1816 Species: Halimeda papyracea Zanardini, 1851 Species: Halimeda peltata Gopinathan & Panigrahy Species: Halimeda pumila Verbruggen, D.S.Littler & M.M.Littler, 2007 Species: Halimeda pygmaea Verbruggen, D.S.Littler & M.M.Littler, 2007 Species: Halimeda rectangularis J.Agardh, 1894 Species: Halimeda renschii Hauck, 1886 Species: Halimeda scabra M.A.Howe, 1905 Species: Halimeda simulans M.A.Howe, 1907 Species: Halimeda stuposa W.R.Taylor, 1950 Species: Halimeda taenicola W.R.Taylor, 1950 Species: Halimeda tuna (J.Ellis & Solander) J.V.Lamouroux, 1816 Species: Halimeda velasquezii W.R.Taylor, 1962 Species: Halimeda xishaensis M.L.Dong & C.K.Tseng, 1980 Species: Halimeda laxa E.S.Barton, 1900 Species: Halimeda platydisca Decaisne, 1842 Species: Halimeda tuna (J.Ellis & Solander) J.V.Lamouroux, 1816 Species: Halimeda tridens (J.Ellis & Solander) J.V.Lamouroux, 1812 = Species: Halimeda incrassata (J.Ellis) J.V.Lamouroux, 1816
