140 MARINE AQUARIA FOR ROOMS. 



same cement may be used as is mentioned when 

 speaking of fresh-water aquaria. The glass sides 

 may be secured by using Collin's patent elastic 

 and marine glue. Rockwork is more indispensable 

 in a tank of this kind than it would be in fresh water, 

 where it is often in the way, rather than otherwise. 

 It ought to be built up in the middle, unless there are 

 reasons to the contrary. Pumice-stone, pieces of mica 



Fig. 99. 



Octagonal Marine Table Tank. 



schist, the slag obtainable from brick-kilns, and oyster 

 shells covered with serpula, are the best kinds of ma- 

 terial, inasmuch as they do not give off anything that 

 will affect the water. The rough surfaces of the pumice- 

 stone and mica soon get greened over with minute and 

 semi-developed algae, and then look very pretty. The 

 rockwork ought to be built in arches and caverns, so 

 that the inhabitants may find shelter from the glare 

 of the too strong light, and cool spots where they can 

 repose. Nearly all the Crustacea shun the light when 



