THE MARINE AQUARIUM 63 



may from time to time arise. If, however, the general hints for 

 the management of the marine aquarium here given be faithfully 

 followed, there ought to be no further losses than must accrue 

 from the injudicious selection of animal species, and these will 

 decrease as experience has been acquired respecting the habits of 

 the creatures introduced. 



We must now pass on to matters pertaining to the mainte- 

 nance of the healthy condition of an aquarium which, we will sup- 

 pose, has been established with due regard to scientific principles. 

 Under this head we shall consider, (1) the aeration of the water, 

 (2) the repair of loss due to evaporation, and (3) the regulation of 

 light and temperature. 



It has already been shown that the marine aquarium can hardly 

 be maintained in a satisfactory condition as regards its air supply 

 by leaving the aeration of the water entirely to the action of plant 

 life ; and herein this form of aquarium differs from that employed 

 for the animal and vegetable life derived from ponds and streams. 

 Fresh-water weeds develop and multiply with such rapidity, and 

 are such ready generators of oxygen gas that it is a very easy 

 matter to establish a fresh-water aquarium that will remain in 

 good condition for years with but little attention ; it is therefore 

 important that we should point out the difference in treatment 

 ueeessary to those of our readers who are already acquainted with 

 the comparative ease with which the fresh- water aquarium may be 

 kept in good order, lest they expect the same self-aerating condi- 

 tion in the marine tank. 



It is never a good plan to leave the renovation of the water of 

 the aquarium until there are visible signs within that something is 

 going wrong. It is true that an unsatisfactory condition of the 

 water, revealed by a slight taint in the odour, or a general turbidity, 

 or the formation of a slight scum on the surface, may sometimes 

 be rectified by the prompt application of some method of artificial 

 aeration, but the aim of the aquarium-keeper should be not the 

 rectification of unsatisfactory conditions, but the establishment of 

 such a method of aeration that the unsatisfactory condition be- 

 comes an impossibility. "We do not wish to discourage anyone 

 who has the slightest desire to start a marine aquarium. Our aim 

 is to point out any difficulties that lie in the way in order that the 

 aquarium may be a success; and thus, having stated that the 

 difficulties attending it are somewhat greater than those connected 

 with the management of a fresh-water aquarium, we should like to 



