44 



NEW YORK AQUARIUM NATURE SERIES 



SKA-LETTUCE (Ulva). 



It is the best aerator for the salt-water aquarium. 

 The red-seaweeds add color and variety and 

 sliould be placed at the bottom of the tank. 



ment already established. It will occasionally be necessary to 

 add water to replace that which escapes by evaporation. This 

 should be done a little at a time and care should be taken to have 

 the temperature the same as that of the water in the tank. 



For the purpose of removing any deposits on the glass of 

 the aquarium, a swab can be made out of a stick with a bit of 

 cheesecloth wrapped about the end. The cloth may be removed 

 each time it is used, which should not be more often than is nec- 

 essary to keep the glass reasonably clean, or if it is used again it 

 should be carefully cleaned and sterilized each time in hot water. 

 The swab will serve not only to remove ordinary dirt, but also 

 the green scum of the minute plant life which in strong light will 

 soon cover the glass. These minute plants do no harm — in fact 

 they are as beneficial in yielding oxygen as are the larger ones — 

 and they are a natural part of the balanced life of the aquarium. 

 Plowever one keeps an aquarium to enjoy the view of its minia- 

 ture water world, and if the green scum interferes with the 

 view it may be removed without great detriment to the adjust- 

 ment. The scum grows thickest on the side nearest the light and 

 it may be allowed to develop on that side as it will serve to 

 screen the strong light somewhat from the animals. 



