4 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The usual method of preparing' artificial sea- water for the aquarium is by use of one 
of the many formulas provided for the purpose. In the present case Turk’s Island salt 
is used. The writer has used this salt for preparing salt water for small still- water 
aquaria with perfect success, and it has proven satisfactory in the present case. There 
was in the beginning some principle, apparently mildly acrid or astringent, affecting 
more or less unfavorably all of the lower forms of life, while it had but little noticeable 
effect on the fishes. Fishes having a slimy mucous coating, such as the toad-fish, 
appeared to lose it and the skin became shriveled in appearance, but their general 
health seemed unaffected. 
It appeared probable that, as there is a considerable precipitate of lime from this 
salt in solution, some of it may have remained in suspension for a long time owing to 
the activity of the circulation. It was noticed at least that in the same water which is 
quiet and has stood for some time the low forms of life kept in much better condition, but 
without some form of aeration the amount of life so kept must be very limited. The 
result was all the more puzzling because of the fact that some fish usually very difficult 
to keep lived remarkably well. Among these was the gizzard shad, transferred from 
fresh water. It was finally found to be necessary to exercise more care in introducing 
the water into the reservoir so as to avoid stirring up the precipitate of lime formed at 
the bottom of the vessel in which the solution was made. After this precaution was 
taken the disturbing effect disappeared. 
It appears, from a paper by E. S. Hoffmann in the Bulletin of the U. S. Fish 
Commission for 1884, that the Berlin, Hamburg, and Vienna aquaria encountered in 
the beginning numerous difficulties in the preparation of artificial sea- water, threaten- 
ing failure for a considerable period. 
The director of the “Zoophyte Aquaria” in the Zoological Garden in Regent’s Park, 
London, declared some years ago that “artificial sea water, even if a chemical analysis 
can not discover the least difference between it and natural sea water, is never bene- 
ficial to animals and plants $” but this has been disproved by the success of the aquaria 
at Berlin, Hamburg, and Vienna. In 1884 the artificially made sea water of the Ham- 
burg aquarium had not been changed for 15 years, and was then perfectly transparent 
and odorless, and in every way satisfactory. 
A minute green organism which appeared in the water of the Washington 
aquarium during a long and unavoidable suspension of the circulation during the 
summer of 1889 in such numbers as to render the water opaque was finally eradicated 
by causing the water to pass through a filter composed of sand and gravel of gradu- 
ated sizes on its way to the reservoir. 
One of the interesting evidences of the advantages of the greenhouse system 
employed, affording abundance of light, is the beginning of the development of algae 
directly from spores on the slate work of the aquaria and on the stones placed therein. 
There is apparent evidence that in time there will be a dense growth of algae adapted 
to the changed conditions, just as on sea-walls, piles, etc. This is a matter of slow 
development in nature, so that some time will elapse, probably, before there is a very 
complete realization of this expectation. 
The necessity for light is most effectually illustrated by the fact that this plant 
development is greatest in the aquaria at the southern end of the grotto, diminishing 
gradually towards the northern end, which does not receive so much sunlight. 
