ECOLOGY AND TAXONOMY OF Halimedu 1 03 



Suitable calcareous materials are quartz gravel, calcareous filtrant 

 material as used in many aquarium systems, Halimeda sand and pieces 

 of cuttle bone. The first two can be obtained from aquarium suppliers, 

 and the second one, the calcareous filtrant, is also available from the 

 suppliers of "Instant Ocean". Halimeda sand is collected in the reef. 

 Cuttle bone, which is only practicable on a small scale, can usually be 

 obtained from pet shops. 



It is not known if a calcareous substrate is necessary for Halimeda 

 growth, but their possession of a calcareous structure suggests that it 

 may be important. The natural populations commonly grow in sand 

 which is largely composed of old Halimeda segments and which is 

 usually highly calcareous. 



Calcareous substrates are washed several times in distilled water 

 before use. 



Sand materials which have been used include reef sand, beach sand 

 and playbox sand. The stand is autoclaved at 15 lb pressure for 20 

 minutes before using. 



(b) Rock substrates. Dead and cleaned coral rock or other soft rock is 

 used partly for substrate, partly for the support and anchorage of rock- 

 growing Halimedae collected with holdfast intact on their own small 

 piece of rock. The rock-growing Halimedae are arranged and supported 

 in a rock framework in such a way that they simulate their natural 

 position in the reef. 



Before being used the rock is washed, and autoclaved for 20 minutes 

 at 15 lb pressure. 



3. Aquaria 



The most used sizes have been 9-5, 11-5 and 191 aquaria which 

 preferably are all-glass. These small sizes are manoeuvrable, and 

 growth can be readily seen and photographed from all sides. Height is a 

 critical dimension in selecting aquaria. One that is too shallow will 

 seriously restrict the size of the thalli selected. A 30 cm height or slightly 

 more would seem close to the ideal unless one is working only with small 

 squat species. This height permits a reasonably thick sand-gravel layer 

 as well as air space at the top which decreases the amount of water 

 bubbling over from changes of pressure in compressed air lines of the 

 circulation system. 



Between uses, aquaria are scrubbed with 10% hydrochloric acid, 

 then filled with tap water and allowed to stand for at least 24 hours. 

 This operation is repeated at least twice more. If possible aquaria are 

 not reused immediately. 



