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TROPICAL AQUARIUM FISHES 9 
or other means, take some fish out of the aquarium. To clear the water 
chemically, add one grain by weight of permanganate of potash (dis- 
solved) to each gallon of aquarium water. This will turn the water first 
a lavender, and then a brownish color for a few days, after which it will 
clear up. Unless the original conditions are changed, however, the water 
will soon again become green. Before using this chemical remove all 
snails and mussels. Goldfish can withstand the strength of the solution 
recommended, and probably be benefitted if suffering from any form of 
fungus. (See Chapter on Diseases.) Other fishes do not stand this 
chemical so well. Green water, while unsightly, is not unwholesome. 
On the contrary, a sick fish is often cured by being transferred to a tank 
of green water. Live daphnia will clear water in a few days. ; 
How to Know When the Fishes are Sick. The first signal of 
distress in most fish is the drooping of the dorsal (back) fin. This fin 
should be carried stiff and upright. When the fish is sick its movements 
are sluggish and it often seeks a quiet corner in which to hide. In some 
of the fancy varieties the dorsal fin is so overdeveloped that the fish even 
in health has not sufficient strength to hold it erect. When such fish are 
ill their fins become more or less stiff, losing flexibility. Fins should be 
clear and clean-cut. When they become thick-looking, opaque, lined with 
red veins, overcast with red, blooshot at base of fins, or ragged and split, 
the fish is in need of attention. (See Chapter on Diseases.) Another 
sign of poor condition is thinness of the body. The excrement of fishes 
in health is usually of a dark color. When it is pale, dotted with gas 
bubbles, and of slimy appearance, the fish is apt to be out of condition. 
Sick Fishes. It is always safer to remove an affected fish from its 
fellows. If the trouble is a contagious one, the aquarium or tank should 
be thoroughly disinfected, not overlooking the plants in this matter. For 
all practical purposes they can be sterilized by placing for one hour in a 
permanganate of potassium solution, 3 grains by weight to the gallon of 
water. Satisfactory results will also be given by dipping plants for a few 
moments in concentrated lime water. Either of these methods should be 
applied to all new plants introduced into the aquarium, especially those 
collected from the wild, or from aquaria of doubtful condition. In case 
of an aquarium becoming contaminated it can be disinfected by dissolving 
in it permanganate of potash to the strength already indicated, allowing 
it to stand from two to three hours, first removing all mussels, snails and 
fishes. In changing back to clear water again it wiJl do no harm if a 
little of the permanganate solution remains. 
Unless newly acquired fishes come from a source beyond suspicion 
it is a grave risk to introduce them at once into an established aquarium 
of healthy fish. They should first be quarantined and carefully observed 
