BULLETIN OP THE UNITED STATES FISH COMMISSION. 467 



tempt may be made with more tender animals, whicb, if placed in the 

 water in the beginning-, wonld probably have died. If no algne can be 

 obtained, the water should be allowed to stand longer. Any one who 

 can aliord to wait until a green cover of algse spreads over the panes, 

 will do well to defer placing the animals in the Avater till that time, and 

 a little patience is very commendable during the entire process. Like 

 wine, salt water, if i)roperly treated, improves with age, as special ap' 

 l^aratus coulinuallj' sui)ply it with oxygen by night, and keep it agi- 

 tated. The water in the Hamburg aquarium has not been changed for 

 fifteen years, and is still perfectly clear, transparent, and odorless, in 

 short, of the very best qualitj' ; and all that has to be done is to make 

 up for accidental losses or evaporation. The water of the salt-water 

 aquarium is changed or filtered onl}' when it begins to get turbid, or if 

 some change is to be made in the arrangement of the aquarium. It 

 will always be advisable, however, to keep at least a double supply of 

 sea- water on hand, and i)lace it in the cellar in well-corked bottles, as 

 any sudden emergency will then be fully met. 



I have never been able to obtain natural sea-water which was as 

 clear as the artificial, through which one can see everything distinctly, 

 even in the most remote corner of a large aquarium, which it would be 

 very difficult to do in natural sea-water. I have brought up sea- water 

 in a dipper, which, when poured into a glass, was as clear as crystal and 

 had a brilliant blue color; but this is possible only on the high-seas, 

 and when the water is brought up from a considerable depth. Fisher- 

 men take too little care and trouble in this respect ; close to the shore 

 they will dip up the water resembling a thick, yellow, and stinking 

 Juice, and ship it to other places. For this reason I use artificial sea- 

 water prepared in the manner indicated above, and even without add- 

 ing any plants, I succeed in keeping my animals alive. 



It is self-evident that the principal point in constructing salt-water 

 aquaria is the treatment of the water, which, after all, is the element which 

 decides the well-being and sickness, life and death of the animals. Care 

 should he takeu to keep the water well supplied with oxygen, which is 

 easily done by means of the aerating apparatus ; and to see to it that 

 the normal proportion between the salts and sea-water is always main- 

 tained, and as soon as anything appears to be wanting in this respect, 

 it should be supplied. As soon as the water begins to get turbid, it 

 should be filtered, and during an abnormal state of the weather it 

 should be cooled. Only when these conditions are fulfilled, will it be 

 possible to keep up a successful saltwater aquarium; only thus shall 

 we be enabled to have in our rooms an exact representation of the 

 bottom of the sea, with all its mysteries and wonders. I, therefore, 

 repeat in conclusion, "The treatment of the water is the main thing." 



Berlin, Germany, Jtdy 22, 1884. 



