Halimeda macroloba (Erect Cactus Alga; Watercress Alga; Money Plant) is a green alga, which grows as clumps of upward-reaching branches formed of a series of calcified round, kidney-shaped segments attached to a large fibrous holdfast. It grows on muddy, sandy or silty bottoms, often forming close-growing mats. Halimeda macroloba reaches a height of 40 cm, and is one of the largest species in the genus. Halimeda macroloba has an extensive range in the Indo-Pacific (from Taiwan to Australia, and the Red Sea to Polynesia). In 2012, it was first collected in Biscayne Bay, where it has spread in the northern portion of the estuary (Ballantine et al. 2023). So far, this is the only known invaded region in the Atlantic. Possible vectors of introduction are ship fouling, including entanglement in rudders, propeller shafts, etc, or aquarium releases. Halimeda spp. are popular in the aquarium trade, although a website says that it has not been reported as cultivated in an aquarium (https://www.reeflex.net/tiere/13677_Halimeda_macroloba.htm.)
Ballantine, David L, Sprung, Julian; Norris , James N. (2023). An Indian Ocean macroalga new to the Atlantic: Halimeda macroloba (Chlorophyta, Halimedaceae) discovered and now established in Biscayne Bay, Florida Bulletin of Marine Science, {missing volume}({missing issue}), Published online. https://doi.org/10.5343/bms.2023.003