20
MAINTAINING FISHES
necessary to aerate the water and then remove the
precipitated iron by employing a sand filter.
SODIUM chloride: Sodium chloride sometimes occm's in well water. There is no satisfactory
means of removing sodium chloride on a large enough
scale practical for aquarium use. Fortunately it is not
highly toxic to most fishes, but its presence makes the
water imsuited for some types of experimental work.
HYDROGEN SULFIDE: Hydrogen sulfide occurs
in well water of some areas. It is highly toxic to fishes
and its removal is usually not practical.
INDUSTRIAL POLLUTANTS: Industrial pollutants are of particular concern when a stream is utilized as a water supply. There are a great number of
industrial pollutants many of which cannot be satisfactorily removed. It is not practical to deal with them
in the present work.
CHLORINE : Chlorine is a serious pollutant of tap
water. It may be removed by heating, aging, chemical treatment, or charcoal filtration. The latter method
is superior to all others. Small, highly successful charcoal filters can be purchased for approximately
$100.00. They may also be built since they consist of
nothing more than a column of animal charcoal (approximately /8 inch particle size) through which water flows at a reduced rate.
Removal of chlorine by heating requires that the
water be held at approximately 180° F. for at least
thirty minutes. Removal by aging requires from four