H. J. WADDINGTON ON MARINE AQUARIA. 243 



sea-water poured in at the back. It is of great advantage to have 

 an extra supply of water. If this is kept in a vessel with fair 

 exposure to light the vegetation which will be formed on the sides 

 will keep it in good condition, and if it becomes necessary to change 

 the water in an aquarium, the bad water may take the place of the 

 water in this stock vessel and will be found in a few hours to have 

 become perfectly good. 



The rockwork for Aquaria, whether made or purchased, requires 

 prolonged soaking in sea-water, once or twice renewed, before it is 

 fit for use. In such a one as I have described, made up rock- 

 work is not requisite, but if desired it should be formed of rook and 

 pumice-stone held together by Portland cement, due care being 

 taken that the density of the rockwork as a whole is greater than 

 that of sea-water. A rockwork that sinks readily in fresh will 

 often float in sea-water. 



It is an erroneous idea that Marine Aquaria require to be of 

 considerable size. The chief advantage of a large aquarium is that 

 it is less likely to be affected by sudden changes of temperature, 

 a larger volume of water naturally requiring more time to become 

 of the external temperature than a smaller volume. Apart from 

 this there is really no limit to the smallness of a perfect aquarium. 

 Many methods will suggest themselves to obviate the difficulty of 

 keeping small Aquaria through the great heat of summer. They 

 may be easily moved into cooler places, while such as are made 

 out of small glass jars, or even ordinary glass tumblers, by readily 

 devised means may be made to float in a larger Aquaria or in pans 

 of ordinary water. By covering the outside with wet flannel, of 

 which a portion is allowed to dip in a vessel of water to ensure 

 constant moisture, I have kept Aquaria perfectly when the heat for 

 days together has been 80°. 



One difficulty is to keep the vegetation within reasonable limits, 

 and to effect this shading from too strong a light must be resorted 

 to. Green baize or some similar material is very useful, but I have 

 found that even with this the vegetation grows too much. Prob- 

 ably a yellow material would have a better effect in checking the 

 growth. I find it more advantageous to allow the vegetation a 

 fair amount of development and to remove it from time to time if 

 excessive, for where there is vegetable vitality, animal vitality 

 follows, and if the vegetation is deficient the animals are sluggish. 



Aeration is not a necessity in a well-ordered aquarium, but is 



