154 MARINE AQUARIA FOR ROOMS. 



rium is about 2 gallons. This is, of course, a great 

 saving of trouble, as with only once attending to 

 it, the water is made to rise to the highest level, and, 

 instead of getting heated in the aquarium by re- 

 maining there, it is drawn off into the darkness again. 

 I think that with this arrangement it is almost im- 

 possible that the water should get foul, except by the 

 grossest neglect." Whenever a. film or scum is seen to 

 settle on the surface of the water, it should be cleared 

 off, either by laying sheets of blotting paper upon it, 

 as you would remove dust, or by drawing off the 

 surface water by means of a syphon. Such a film 

 hinders the free passage of air to the water, and Mr. 

 Lloyd has shown that water has a stronger affinity 

 for the oxygen of the atmosphere it is in contact with 

 than its nitrogen. 



The regulation of the light and temperature of 

 marine tanks is quite as important a task as in the 

 management of fresh-water aquaria, if not more so. 



Their temperature should always be low, so that 

 the water feels cold to the hand. It should, however, 

 never fall below forty degrees Fahrenheit. If the 

 tank be so placed that it is difficult to prevent the 

 heat unduly warming it, a small piece of ice may 

 be placed in the water to replace that lost by eva- 

 poration. Light is perhaps even more to be stu- 

 died than temperature, as it stimulates the growth 

 of the well-known green confervae which are such a 

 source of trouble to the uninitiated. If the light and 



