Page:Popular Science Monthly Volume 78.djvu/609

Rh allowed a volume of water of 1 dm3. Carnivorous fishes, crustaceans and aquatic insects must be of about the same size and only a few in each aquarium. To avoid cannibalism the parents must be separated from the eggs, or spawn and the young, except when the parents brood their offspring. Comparatively small vessels are sufficient for indolent forms like tadpoles, salamanders, aquatic insects and most crustaceans. In most cases when breeding, the larger the tank the more certain the result and the more numerous the progeny. Some animals need stagnant slowly flowing water, others a rapid current, some always live in the water, others only during certain times of the year and still others only during certain stages in the life history. Sharp-angled stones are

necessary for certain fishes and amphibia to scrape against in order to remove from their skins such deadly enemies as the fungus Saprolegnia. The annual natural range of temperature must be followed, especially in the breeding of animals. Inhabitants of stagnant pools require a range from 4°-35° C, those of slowly flowing, shallow waters 4°25° C, of the greater depths 4°-18° C, of rushing, rough mountain brooks with shallow places 4°-15*' C. and of caves 12°-17° C. Carnivorous animals need be fed only every other day, and because of the restricted movement in confinement overfeeding leads to fatty degeneration, especially of the reproductive organs. If diseases appear the sick animals must be isolated and the aquaria very carefully cleansed with hot water and the use of disinfectants. Saprolegnia and