10
MAINTAINING FISHES
are produced by decay and as waste products from
fishes. These can be prevented from accumulating
by aeration and charcoal filtration.
The accumulation of soluble salts both by evaporation and from excretion is best avoided by frequently replacing a portion of the water of each tank
or by continuously flushing the tanks.
The repression of reproduction appears to become
evident when populations are unusually dense. Thianing a population is an obvious approach. Continuous
flushing may also be a solution.
Growth repression may function at a much lower
level of population density than reproduction repression. The author does not feel that enough is known
about this phenomenon to make possible recommendations for avoiding it.
Classification of Fish-holding Facilities
In order to increase the grams of fish per liter of
water, the following artificial aids are commonly used:
frequent water changes, aeration, filtering and flushing. Whether or not artificial aids are used and to
what extent will considerably affect the physicochemical conditions of the aquarium water. The variation in artificial aids in maintaining desirable
aquarium conditions must be recognized in deciding
what type of set-up is best suited to a particular need.
We, thus, may consider the different arrangements
one might set up and the use to which they are best
suited.
The first and simplest arrangement involves no replacement or artificial aids for neutralizing wastes and
replenishing oxygen. The weight of fish to volume of