164 L. HILLIS-COLINVAUX 



4. Circulation system 



In the small 11-51 aquaria used most frequently, circulation is 

 provided by aquarium air-bubblers, sometimes with the addition of an 

 outside or inside water-filtermg system. 



Long air bubblers (approximately 14 cm) are connected to a com- 

 pressed air system by Teflon tubing. An air-filter system of glass-wool 

 is interposed, and a manifold is used so that several aquaria may feed 

 off the system. Rate of flow to individual aquaria is regulated by 

 C-clamps on the Teflon leads to each aquarium. The particular bubblers 

 used function well after autoclaving. 



A closed- circuit water-filtering system is sometimes used by adding 

 the standard inside or outside aquarium filter, fitted only with glass- 

 wool, which fits against the vertical walls of the aquaria. Bottom or 

 under-gravel filters might be feasible for Halimedae which grow on 

 rocks or sprawl but are not suitable for sand-growing species. The 

 Rhipsalian Halimedae do not normally have water circulating past their 

 holdfast systems, which, in some reef sites, even grow in an anoxic 

 environment. The reducing environment may facilitate the exchange of 

 certain ions between substrate and holdfast, with such reactions bemg 

 important to the successful growth of these particular species. 



5. Temperature control 



Kinsman (1964) gives a range of 25-29 °C as the temperature at 

 which reef corals best flourish, while indicating that these organisms 

 can withstand limited exposure to 16-17 °C, and that some corals 

 contmue to grow at temperatures as high as 36 °C. 



For Halimeda, temperatures of 27-29 °C are probably about optimal, 

 although these plants are exposed to higher and lower temperatures in 

 the reef. A range of approximately 25-29 °C is acceptable. 



Lighting will increase the water temperature of the small aquaria by 

 2 °C and more, depending on the intensity and duration. 



6. Light intensity and cycle 



Light intensities for much of the Halimeda culturing have ranged 

 from 375 to 780 foot-candles, measured just above the sand-water 

 interface. Intensities as low as 100 ft-c have been used, but growth is 

 very slow or absent. 



Lighting on a 12-hour light : 12-hour dark cycle is provided by 

 cool- white fluorescent light placed about 22 cm above the aquaria. The 

 lighting cycle was chosen because it is that of the tropics. 



