CONDITIONS OF LIGHT, ETC. 
ROCKWORK FOR THE AQUARIUM 
Picturesque effects in the aquarium may be produced by the introduc- 
tion of rockwork and other natural objects. Pomice adapts itself well for 
this purpose and is easily worked. Odd pieces fastened together to form 
a grotto or rockery may have the surfaces hollowed out to contain soil 
and sand in which plants may be grown, or form a screen behind which 
brackets for small flower pots may be constructed. ‘Tuftstone is also to 
be recommended, as very handsome odd pieces may be obtained and nat- 
ural effects produced by their tasteful arrangement. Selinite or gypsum 
nay be introduced, as it is not only handsome in appearance but dissolv- 
ing slowly in the water, it furnishes lime, necessary to the molluscs and 
other animal life. Small pieces of plaster of paris will also serve for this 
purpose. Mica schist, quartz, feldspar, agate, rock crystals and other 
minerals are effective, or water-worn stones to which aquatic plants are 
attached may be introduced, but all other objects not natural to a water 
garden are in questionable taste. All objects should be clean, and soaked 
for some time in water before they are put into the aquarium. 
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