8 
BULLETIN OF THE UNITED STATES FISH COMMISSION 
brackish water was noticed, it was impossible to restrict its ravages. When thus 
infested the fish will refuse food and by scratching themselves violently on the sand 
or stones will soon produce an inflamed condition of the skin and a rapid growth of 
fungus, to which influences they soon yield and die. 
The necessity for a supply of brackish water in circulation, in addition to the salt 
and fresh water system, is thus demonstrated to be of the greatest importance, from a 
practical and economical standpoint. 
The prevailing muddy character of Potomac River water renders it necessary to 
employ some means of filtration. The system now in use (the Loomis), although prob- 
ably as good as any, if not the best of the same character in use, is open to serious 
objections from several points of view. It requires frequent cleaning to render constant 
good service. The use of alum as a coagulator involves the necessity of very great 
watchfulness on the part of those required to attend to the operation of the filter. 
The amount of alum dissolved, or necessary to take up the matter in suspension in the 
water, appears to vary somewhat with temperature. The muddying and clearing of 
the water must be closely watched and the alum feed regulated to correspond. A very 
slight amount of alum will affect fish, and accidents will occur with the most watchful 
under such circumstances. 
There is a question also as to whether, although apparently having no direct injurious 
action on the fish, something in the character of the water after filtration by the alum 
process may not be, in part at least, the cause of the difficulties encountered from fungus. 
It is stated in the Report of Walpole and Huxley, inspectors of fisheries of England 
and Wales, for 1881 (See Bull. TJ. S. Fish Com. 1881), that — 
It is known with respect to many of the common molds such as Penicillium and Mucor, which 
are habitually saprophytes (that is to say, live on decaying organic matter as Saprolegnia does), that 
they flourish in certain artificial solutions containing salts of ammonia. It is quite possible, though 
whether the fact is so will have to he experimentally determined, that Saprolegnia is capable of living- 
under the same conditions. Fungi are also extremely sensitive to slight differences in the acidity or 
alkalinity of water, so that even apparently insignificant changes in that respect may come into play 
as secondary conditions of salmon disease. * * * A factory for making a spirit from turnips was 
established near Schweidnitz, in Silesia, and the refuse was poured into an affluent of the river West- 
nitz, which runs by Schweidnitz. The result was such a prodigious growth of Leptometus that the 
fungus covered some 10,000 square feet of the bottom of the stream with a thick white layer compared 
to sheep’s fleeces, choked up the pipes, and rendered the water of the town undrinkable. 
The writer has noticed similar developments of fungus, possibly the same, in streams 
into which the refuse of creameries was allowed to drain. On the other hand, the 
presence of fungus in such quantities in the fresh- water tanks at Central Station may be 
due, to a great extent, to the lack of light afforded them and the consequent absence of 
growing aquatic plants, as in those tanks where there is an abundance of light and a 
healthy plant growth it gives no trouble, in fact is practically unknown. 
The attempts to establish an exhibit of live fishes at the New Orleans Exhibition 
failed because of the use of alum in filtration. At the Ohio Valley Exposition, at 
Cincinnati, Ohio, in 1888, very great difficulties were encountered in establishing an 
exhibit of aquaria, owing to the muddy character of Ohio River water and the high 
pressure of the water supply there. Some accidents occurring threatened for a time a 
failure of the live-fish exhibit. The difficulties were finally overcome, but, together 
with the other experiences and observations herein recorded, point to the desirability 
